// SPDX-License-Identifier: MIT
pragma solidity 0.6.12;
import "./interfaces/MathUtil.sol";
import "./interfaces/ILockedCvx.sol";
import '@openzeppelin/contracts/token/ERC20/IERC20.sol';
import '@openzeppelin/contracts/token/ERC20/SafeERC20.sol';
import '@openzeppelin/contracts/math/SafeMath.sol';
interface IBasicRewards{
    function getReward(address _account, bool _claimExtras) external;
    function getReward(address _account) external;
    function getReward(address _account, address _token) external;
    function stakeFor(address, uint256) external;
}
interface ICvxRewards{
    function getReward(address _account, bool _claimExtras, bool _stake) external;
}
interface IChefRewards{
    function claim(uint256 _pid, address _account) external;
}
interface ICvxCrvDeposit{
    function deposit(uint256, bool) external;
}
interface ISwapExchange {
    function exchange(
        int128,
        int128,
        uint256,
        uint256
    ) external returns (uint256);
}
//Claim zap to bundle various reward claims
//v2:
// - change exchange to use curve pool
// - add getReward(address,token) type
// - add option to lock cvx
// - add option use all funds in wallet
contract ClaimZap{
    using SafeERC20 for IERC20;
    using SafeMath for uint256;
    address public constant crv = address(0xD533a949740bb3306d119CC777fa900bA034cd52);
    address public constant cvx = address(0x4e3FBD56CD56c3e72c1403e103b45Db9da5B9D2B);
    address public constant cvxCrv = address(0x62B9c7356A2Dc64a1969e19C23e4f579F9810Aa7);
    address public constant crvDeposit = address(0x8014595F2AB54cD7c604B00E9fb932176fDc86Ae);
    address public constant cvxRewards = address(0xCF50b810E57Ac33B91dCF525C6ddd9881B139332);
    address public constant exchange = address(0x9D0464996170c6B9e75eED71c68B99dDEDf279e8);//curve
    address public constant locker = address(0x72a19342e8F1838460eBFCCEf09F6585e32db86E);
    address public immutable cvxCrvRewards;
    address public immutable owner;
    enum Options{
        ClaimCvx, //1
        ClaimCvxAndStake, //2
        ClaimCvxCrv, //4
        ClaimLockedCvx, //8
        ClaimLockedCvxStake, //16
        LockCrvDeposit, //32
        UseAllWalletFunds, //64
        LockCvx //128
    }
    constructor(address _cvxcrvStaking) public {
        owner = msg.sender;
        cvxCrvRewards = _cvxcrvStaking;
    }
    //2.1 - change cvxcrv staking address as immutable in constructor, change claim parameters
    function getName() external pure returns (string memory) {
        return "ClaimZap V2.1";
    }
    function setApprovals() external {
        require(msg.sender == owner, "!auth");
        IERC20(crv).safeApprove(crvDeposit, 0);
        IERC20(crv).safeApprove(crvDeposit, uint256(-1));
        IERC20(crv).safeApprove(exchange, 0);
        IERC20(crv).safeApprove(exchange, uint256(-1));
        IERC20(cvx).safeApprove(cvxRewards, 0);
        IERC20(cvx).safeApprove(cvxRewards, uint256(-1));
        IERC20(cvxCrv).safeApprove(cvxCrvRewards, 0);
        IERC20(cvxCrv).safeApprove(cvxCrvRewards, uint256(-1));
        IERC20(cvx).safeApprove(locker, 0);
        IERC20(cvx).safeApprove(locker, uint256(-1));
    }
    function CheckOption(uint256 _mask, uint256 _flag) internal pure returns(bool){
        return (_mask & (1<<_flag)) != 0;
    }
    function claimRewards(
        address[] calldata rewardContracts,
        address[] calldata extraRewardContracts,
        address[] calldata tokenRewardContracts,
        address[] calldata tokenRewardTokens,
        uint256 depositCrvMaxAmount,
        uint256 minAmountOut,
        uint256 depositCvxMaxAmount,
        uint256 spendCvxAmount,
        uint256 options
        ) external{
        uint256 crvBalance = IERC20(crv).balanceOf(msg.sender);
        uint256 cvxBalance = IERC20(cvx).balanceOf(msg.sender);
 
        //claim from main curve LP pools
        for(uint256 i = 0; i < rewardContracts.length; i++){
            IBasicRewards(rewardContracts[i]).getReward(msg.sender,true);
        }
        //claim from extra rewards
        for(uint256 i = 0; i < extraRewardContracts.length; i++){
            IBasicRewards(extraRewardContracts[i]).getReward(msg.sender);
        }
        //claim from multi reward token contract
        for(uint256 i = 0; i < tokenRewardContracts.length; i++){
            IBasicRewards(tokenRewardContracts[i]).getReward(msg.sender,tokenRewardTokens[i]);
        }
        //claim others/deposit/lock/stake
        _claimExtras(depositCrvMaxAmount,minAmountOut,depositCvxMaxAmount,spendCvxAmount,crvBalance,cvxBalance,options);
    }
    function _claimExtras(
        uint256 depositCrvMaxAmount,
        uint256 minAmountOut,
        uint256 depositCvxMaxAmount,
        uint256 spendCvxAmount,
        uint256 removeCrvBalance,
        uint256 removeCvxBalance,
        uint256 options
        ) internal{
        //claim (and stake) from cvx rewards
        if(CheckOption(options,uint256(Options.ClaimCvxAndStake))){
            ICvxRewards(cvxRewards).getReward(msg.sender,true,true);
        }else if(CheckOption(options,uint256(Options.ClaimCvx))){
            ICvxRewards(cvxRewards).getReward(msg.sender,true,false);
        }
        //claim from cvxCrv rewards
        if(CheckOption(options,uint256(Options.ClaimCvxCrv))){
            IBasicRewards(cvxCrvRewards).getReward(msg.sender);
        }
        //claim from locker
        if(CheckOption(options,uint256(Options.ClaimLockedCvx))){
            ILockedCvx(locker).getReward(msg.sender,CheckOption(options,uint256(Options.ClaimLockedCvxStake)));
        }
        //reset remove balances if we want to also stake/lock funds already in our wallet
        if(CheckOption(options,uint256(Options.UseAllWalletFunds))){
            removeCrvBalance = 0;
            removeCvxBalance = 0;
        }
        //lock upto given amount of crv and stake
        if(depositCrvMaxAmount > 0){
            uint256 crvBalance = IERC20(crv).balanceOf(msg.sender).sub(removeCrvBalance);
            crvBalance = MathUtil.min(crvBalance, depositCrvMaxAmount);
            if(crvBalance > 0){
                //pull crv
                IERC20(crv).safeTransferFrom(msg.sender, address(this), crvBalance);
                if(minAmountOut > 0){
                    //swap
                    ISwapExchange(exchange).exchange(0,1,crvBalance,minAmountOut);
                }else{
                    //deposit
                    ICvxCrvDeposit(crvDeposit).deposit(crvBalance,CheckOption(options,uint256(Options.LockCrvDeposit)));
                }
                //get cvxcrv amount
                uint256 cvxCrvBalance = IERC20(cvxCrv).balanceOf(address(this));
                //stake for msg.sender
                IBasicRewards(cvxCrvRewards).stakeFor(msg.sender, cvxCrvBalance);
            }
        }
        //stake up to given amount of cvx
        if(depositCvxMaxAmount > 0){
            uint256 cvxBalance = IERC20(cvx).balanceOf(msg.sender).sub(removeCvxBalance);
            cvxBalance = MathUtil.min(cvxBalance, depositCvxMaxAmount);
            if(cvxBalance > 0){
                //pull cvx
                IERC20(cvx).safeTransferFrom(msg.sender, address(this), cvxBalance);
                if(CheckOption(options,uint256(Options.LockCvx))){
                    ILockedCvx(locker).lock(msg.sender, cvxBalance, spendCvxAmount);
                }else{
                    //stake for msg.sender
                    IBasicRewards(cvxRewards).stakeFor(msg.sender, cvxBalance);
                }
            }
        }
    }
}// SPDX-License-Identifier: MIT
pragma solidity 0.6.12;
/**
 * @dev Standard math utilities missing in the Solidity language.
 */
library MathUtil {
    /**
     * @dev Returns the smallest of two numbers.
     */
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }
}// SPDX-License-Identifier: MIT
pragma solidity 0.6.12;
pragma experimental ABIEncoderV2;
interface ILockedCvx{
     struct LockedBalance {
        uint112 amount;
        uint112 boosted;
        uint32 unlockTime;
    }
    function lock(address _account, uint256 _amount, uint256 _spendRatio) external;
    function processExpiredLocks(bool _relock) external;
    function getReward(address _account, bool _stake) external;
    function balanceAtEpochOf(uint256 _epoch, address _user) view external returns(uint256 amount);
    function totalSupplyAtEpoch(uint256 _epoch) view external returns(uint256 supply);
    function epochCount() external view returns(uint256);
    function epochs(uint256 _id) external view returns(uint224,uint32);
    function checkpointEpoch() external;
    function balanceOf(address _account) external view returns(uint256);
    function lockedBalanceOf(address _user) external view returns(uint256 amount);
    function pendingLockOf(address _user) external view returns(uint256 amount);
    function pendingLockAtEpochOf(uint256 _epoch, address _user) view external returns(uint256 amount);
    function totalSupply() view external returns(uint256 supply);
    function lockedBalances(
        address _user
    ) view external returns(
        uint256 total,
        uint256 unlockable,
        uint256 locked,
        LockedBalance[] memory lockData
    );
    function addReward(
        address _rewardsToken,
        address _distributor,
        bool _useBoost
    ) external;
    function approveRewardDistributor(
        address _rewardsToken,
        address _distributor,
        bool _approved
    ) external;
    function setStakeLimits(uint256 _minimum, uint256 _maximum) external;
    function setBoost(uint256 _max, uint256 _rate, address _receivingAddress) external;
    function setKickIncentive(uint256 _rate, uint256 _delay) external;
    function shutdown() external;
    function recoverERC20(address _tokenAddress, uint256 _tokenAmount) external;
}// SPDX-License-Identifier: MIT
pragma solidity >=0.6.2 <0.8.0;
/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.
        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }
    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");
        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{ value: amount }("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }
    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }
    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");
        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: value }(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data, string memory errorMessage) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");
        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");
        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }
    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly
                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
import "./IERC20.sol";
import "../../math/SafeMath.sol";
import "../../utils/Address.sol";
/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using SafeMath for uint256;
    using Address for address;
    function safeTransfer(IERC20 token, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }
    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }
    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(IERC20 token, address spender, uint256 value) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }
    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).add(value);
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }
    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }
    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.
        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);
    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);
    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);
    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);
    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);
    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);
    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }
    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b > a) return (false, 0);
        return (true, a - b);
    }
    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) return (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }
    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }
    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");
        return c;
    }
    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a, "SafeMath: subtraction overflow");
        return a - b;
    }
    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) return 0;
        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");
        return c;
    }
    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }
    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: modulo by zero");
        return a % b;
    }
    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        return a - b;
    }
    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a / b;
    }
    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a % b;
    }
}

// File: contracts\interfaces\MathUtil.sol

// SPDX-License-Identifier: MIT
pragma solidity 0.6.12;

/**
 * @dev Standard math utilities missing in the Solidity language.
 */
library MathUtil {
    /**
     * @dev Returns the smallest of two numbers.
     */
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }
}

// File: contracts\interfaces\IStakingProxy.sol

pragma solidity 0.6.12;

interface IStakingProxy {
    function getBalance() external view returns(uint256);

    function withdraw(uint256 _amount) external;

    function stake() external;

    function distribute() external;
}

// File: contracts\interfaces\IRewardStaking.sol

pragma solidity 0.6.12;

interface IRewardStaking {
    function stakeFor(address, uint256) external;
    function stake( uint256) external;
    function withdraw(uint256 amount, bool claim) external;
    function withdrawAndUnwrap(uint256 amount, bool claim) external;
    function earned(address account) external view returns (uint256);
    function getReward() external;
    function getReward(address _account, bool _claimExtras) external;
    function extraRewardsLength() external view returns (uint256);
    function extraRewards(uint256 _pid) external view returns (address);
    function rewardToken() external view returns (address);
    function balanceOf(address _account) external view returns (uint256);
}

// File: contracts\interfaces\BoringMath.sol

pragma solidity 0.6.12;

/// @notice A library for performing overflow-/underflow-safe math,
/// updated with awesomeness from of DappHub (https://github.com/dapphub/ds-math).
library BoringMath {
    function add(uint256 a, uint256 b) internal pure returns (uint256 c) {
        require((c = a + b) >= b, "BoringMath: Add Overflow");
    }

    function sub(uint256 a, uint256 b) internal pure returns (uint256 c) {
        require((c = a - b) <= a, "BoringMath: Underflow");
    }

    function mul(uint256 a, uint256 b) internal pure returns (uint256 c) {
        require(b == 0 || (c = a * b) / b == a, "BoringMath: Mul Overflow");
    }

    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "BoringMath: division by zero");
        return a / b;
    }

    function to128(uint256 a) internal pure returns (uint128 c) {
        require(a <= uint128(-1), "BoringMath: uint128 Overflow");
        c = uint128(a);
    }

    function to64(uint256 a) internal pure returns (uint64 c) {
        require(a <= uint64(-1), "BoringMath: uint64 Overflow");
        c = uint64(a);
    }

    function to32(uint256 a) internal pure returns (uint32 c) {
        require(a <= uint32(-1), "BoringMath: uint32 Overflow");
        c = uint32(a);
    }

    function to40(uint256 a) internal pure returns (uint40 c) {
        require(a <= uint40(-1), "BoringMath: uint40 Overflow");
        c = uint40(a);
    }

    function to112(uint256 a) internal pure returns (uint112 c) {
        require(a <= uint112(-1), "BoringMath: uint112 Overflow");
        c = uint112(a);
    }

    function to224(uint256 a) internal pure returns (uint224 c) {
        require(a <= uint224(-1), "BoringMath: uint224 Overflow");
        c = uint224(a);
    }

    function to208(uint256 a) internal pure returns (uint208 c) {
        require(a <= uint208(-1), "BoringMath: uint208 Overflow");
        c = uint208(a);
    }

    function to216(uint256 a) internal pure returns (uint216 c) {
        require(a <= uint216(-1), "BoringMath: uint216 Overflow");
        c = uint216(a);
    }
}

/// @notice A library for performing overflow-/underflow-safe addition and subtraction on uint128.
library BoringMath128 {
    function add(uint128 a, uint128 b) internal pure returns (uint128 c) {
        require((c = a + b) >= b, "BoringMath: Add Overflow");
    }

    function sub(uint128 a, uint128 b) internal pure returns (uint128 c) {
        require((c = a - b) <= a, "BoringMath: Underflow");
    }
}

/// @notice A library for performing overflow-/underflow-safe addition and subtraction on uint64.
library BoringMath64 {
    function add(uint64 a, uint64 b) internal pure returns (uint64 c) {
        require((c = a + b) >= b, "BoringMath: Add Overflow");
    }

    function sub(uint64 a, uint64 b) internal pure returns (uint64 c) {
        require((c = a - b) <= a, "BoringMath: Underflow");
    }
}

/// @notice A library for performing overflow-/underflow-safe addition and subtraction on uint32.
library BoringMath32 {
    function add(uint32 a, uint32 b) internal pure returns (uint32 c) {
        require((c = a + b) >= b, "BoringMath: Add Overflow");
    }

    function sub(uint32 a, uint32 b) internal pure returns (uint32 c) {
        require((c = a - b) <= a, "BoringMath: Underflow");
    }

    function mul(uint32 a, uint32 b) internal pure returns (uint32 c) {
        require(b == 0 || (c = a * b) / b == a, "BoringMath: Mul Overflow");
    }

    function div(uint32 a, uint32 b) internal pure returns (uint32) {
        require(b > 0, "BoringMath: division by zero");
        return a / b;
    }
}


/// @notice A library for performing overflow-/underflow-safe addition and subtraction on uint112.
library BoringMath112 {
    function add(uint112 a, uint112 b) internal pure returns (uint112 c) {
        require((c = a + b) >= b, "BoringMath: Add Overflow");
    }

    function sub(uint112 a, uint112 b) internal pure returns (uint112 c) {
        require((c = a - b) <= a, "BoringMath: Underflow");
    }

    function mul(uint112 a, uint112 b) internal pure returns (uint112 c) {
        require(b == 0 || (c = a * b) / b == a, "BoringMath: Mul Overflow");
    }
    
    function div(uint112 a, uint112 b) internal pure returns (uint112) {
        require(b > 0, "BoringMath: division by zero");
        return a / b;
    }
}

/// @notice A library for performing overflow-/underflow-safe addition and subtraction on uint224.
library BoringMath224 {
    function add(uint224 a, uint224 b) internal pure returns (uint224 c) {
        require((c = a + b) >= b, "BoringMath: Add Overflow");
    }

    function sub(uint224 a, uint224 b) internal pure returns (uint224 c) {
        require((c = a - b) <= a, "BoringMath: Underflow");
    }

    function mul(uint224 a, uint224 b) internal pure returns (uint224 c) {
        require(b == 0 || (c = a * b) / b == a, "BoringMath: Mul Overflow");
    }
    
    function div(uint224 a, uint224 b) internal pure returns (uint224) {
        require(b > 0, "BoringMath: division by zero");
        return a / b;
    }
}

// File: @openzeppelin\contracts\token\ERC20\IERC20.sol

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

// File: @openzeppelin\contracts\math\SafeMath.sol

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b > a) return (false, 0);
        return (true, a - b);
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) return (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }

    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");
        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a, "SafeMath: subtraction overflow");
        return a - b;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) return 0;
        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");
        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: modulo by zero");
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        return a - b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a % b;
    }
}

// File: @openzeppelin\contracts\utils\Address.sol
pragma solidity >=0.6.2 <0.8.0;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{ value: amount }("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: value }(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data, string memory errorMessage) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// File: @openzeppelin\contracts\token\ERC20\SafeERC20.sol
pragma solidity >=0.6.0 <0.8.0;



/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using SafeMath for uint256;
    using Address for address;

    function safeTransfer(IERC20 token, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(IERC20 token, address spender, uint256 value) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).add(value);
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

// File: @openzeppelin\contracts\math\Math.sol

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Standard math utilities missing in the Solidity language.
 */
library Math {
    /**
     * @dev Returns the largest of two numbers.
     */
    function max(uint256 a, uint256 b) internal pure returns (uint256) {
        return a >= b ? a : b;
    }

    /**
     * @dev Returns the smallest of two numbers.
     */
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }

    /**
     * @dev Returns the average of two numbers. The result is rounded towards
     * zero.
     */
    function average(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b) / 2 can overflow, so we distribute
        return (a / 2) + (b / 2) + ((a % 2 + b % 2) / 2);
    }
}

// File: @openzeppelin\contracts\utils\Context.sol
pragma solidity >=0.6.0 <0.8.0;

/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with GSN meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

// File: @openzeppelin\contracts\access\Ownable.sol

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor () internal {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), msgSender);
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

// File: @openzeppelin\contracts\utils\ReentrancyGuard.sol

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
abstract contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor () internal {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and make it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        // On the first call to nonReentrant, _notEntered will be true
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;

        _;

        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }
}

// File: contracts\CvxLockerV2.sol

pragma solidity 0.6.12;
pragma experimental ABIEncoderV2;
/*
CVX Locking contract for https://www.convexfinance.com/
CVX locked in this contract will be entitled to voting rights for the Convex Finance platform
Based on EPS Staking contract for http://ellipsis.finance/
Based on SNX MultiRewards by iamdefinitelyahuman - https://github.com/iamdefinitelyahuman/multi-rewards

V2:
- change locking mechanism to lock to a future epoch instead of current
- pending lock getter
- relocking allocates weight to the current epoch instead of future,
    thus allows keeping voting weight in the same epoch a lock expires by relocking before a vote begins
- balanceAtEpoch and supplyAtEpoch return proper values for future epochs
- do not allow relocking directly to a new address
*/
contract CvxLockerV2 is ReentrancyGuard, Ownable {

    using BoringMath for uint256;
    using BoringMath224 for uint224;
    using BoringMath112 for uint112;
    using BoringMath32 for uint32;
    using SafeERC20
    for IERC20;

    /* ========== STATE VARIABLES ========== */

    struct Reward {
        bool useBoost;
        uint40 periodFinish;
        uint208 rewardRate;
        uint40 lastUpdateTime;
        uint208 rewardPerTokenStored;
    }
    struct Balances {
        uint112 locked;
        uint112 boosted;
        uint32 nextUnlockIndex;
    }
    struct LockedBalance {
        uint112 amount;
        uint112 boosted;
        uint32 unlockTime;
    }
    struct EarnedData {
        address token;
        uint256 amount;
    }
    struct Epoch {
        uint224 supply; //epoch boosted supply
        uint32 date; //epoch start date
    }

    //token constants
    IERC20 public constant stakingToken = IERC20(0x4e3FBD56CD56c3e72c1403e103b45Db9da5B9D2B); //cvx
    address public constant cvxCrv = address(0x62B9c7356A2Dc64a1969e19C23e4f579F9810Aa7);

    //rewards
    address[] public rewardTokens;
    mapping(address => Reward) public rewardData;

    // Duration that rewards are streamed over
    uint256 public constant rewardsDuration = 86400 * 7;

    // Duration of lock/earned penalty period
    uint256 public constant lockDuration = rewardsDuration * 16;

    // reward token -> distributor -> is approved to add rewards
    mapping(address => mapping(address => bool)) public rewardDistributors;

    // user -> reward token -> amount
    mapping(address => mapping(address => uint256)) public userRewardPerTokenPaid;
    mapping(address => mapping(address => uint256)) public rewards;

    //supplies and epochs
    uint256 public lockedSupply;
    uint256 public boostedSupply;
    Epoch[] public epochs;

    //mappings for balance data
    mapping(address => Balances) public balances;
    mapping(address => LockedBalance[]) public userLocks;

    //boost
    address public boostPayment = address(0x1389388d01708118b497f59521f6943Be2541bb7);
    uint256 public maximumBoostPayment = 0;
    uint256 public boostRate = 10000;
    uint256 public nextMaximumBoostPayment = 0;
    uint256 public nextBoostRate = 10000;
    uint256 public constant denominator = 10000;

    //staking
    uint256 public minimumStake = 10000;
    uint256 public maximumStake = 10000;
    address public stakingProxy;
    address public constant cvxcrvStaking = address(0x3Fe65692bfCD0e6CF84cB1E7d24108E434A7587e);
    uint256 public constant stakeOffsetOnLock = 500; //allow broader range for staking when depositing

    //management
    uint256 public kickRewardPerEpoch = 100;
    uint256 public kickRewardEpochDelay = 4;

    //shutdown
    bool public isShutdown = false;

    //erc20-like interface
    string private _name;
    string private _symbol;
    uint8 private immutable _decimals;

    /* ========== CONSTRUCTOR ========== */

    constructor() public Ownable() {
        _name = "Vote Locked Convex Token";
        _symbol = "vlCVX";
        _decimals = 18;

        uint256 currentEpoch = block.timestamp.div(rewardsDuration).mul(rewardsDuration);
        epochs.push(Epoch({
            supply: 0,
            date: uint32(currentEpoch)
        }));
    }

    function decimals() public view returns (uint8) {
        return _decimals;
    }
    function name() public view returns (string memory) {
        return _name;
    }
    function symbol() public view returns (string memory) {
        return _symbol;
    }
    function version() public view returns(uint256){
        return 2;
    }

    /* ========== ADMIN CONFIGURATION ========== */

    // Add a new reward token to be distributed to stakers
    function addReward(
        address _rewardsToken,
        address _distributor,
        bool _useBoost
    ) public onlyOwner {
        require(rewardData[_rewardsToken].lastUpdateTime == 0);
        require(_rewardsToken != address(stakingToken));
        rewardTokens.push(_rewardsToken);
        rewardData[_rewardsToken].lastUpdateTime = uint40(block.timestamp);
        rewardData[_rewardsToken].periodFinish = uint40(block.timestamp);
        rewardData[_rewardsToken].useBoost = _useBoost;
        rewardDistributors[_rewardsToken][_distributor] = true;
    }

    // Modify approval for an address to call notifyRewardAmount
    function approveRewardDistributor(
        address _rewardsToken,
        address _distributor,
        bool _approved
    ) external onlyOwner {
        require(rewardData[_rewardsToken].lastUpdateTime > 0);
        rewardDistributors[_rewardsToken][_distributor] = _approved;
    }

    //Set the staking contract for the underlying cvx
    function setStakingContract(address _staking) external onlyOwner {
        require(stakingProxy == address(0), "!assign");

        stakingProxy = _staking;
    }

    //set staking limits. will stake the mean of the two once either ratio is crossed
    function setStakeLimits(uint256 _minimum, uint256 _maximum) external onlyOwner {
        require(_minimum <= denominator, "min range");
        require(_maximum <= denominator, "max range");
        require(_minimum <= _maximum, "min range");
        minimumStake = _minimum;
        maximumStake = _maximum;
        updateStakeRatio(0);
    }

    //set boost parameters
    function setBoost(uint256 _max, uint256 _rate, address _receivingAddress) external onlyOwner {
        require(_max < 1500, "over max payment"); //max 15%
        require(_rate < 30000, "over max rate"); //max 3x
        require(_receivingAddress != address(0), "invalid address"); //must point somewhere valid
        nextMaximumBoostPayment = _max;
        nextBoostRate = _rate;
        boostPayment = _receivingAddress;
    }

    //set kick incentive
    function setKickIncentive(uint256 _rate, uint256 _delay) external onlyOwner {
        require(_rate <= 500, "over max rate"); //max 5% per epoch
        require(_delay >= 2, "min delay"); //minimum 2 epochs of grace
        kickRewardPerEpoch = _rate;
        kickRewardEpochDelay = _delay;
    }

    //shutdown the contract. unstake all tokens. release all locks
    function shutdown() external onlyOwner {
        if (stakingProxy != address(0)) {
            uint256 stakeBalance = IStakingProxy(stakingProxy).getBalance();
            IStakingProxy(stakingProxy).withdraw(stakeBalance);
        }
        isShutdown = true;
    }

    //set approvals for staking cvx and cvxcrv
    function setApprovals() external {
        IERC20(cvxCrv).safeApprove(cvxcrvStaking, 0);
        IERC20(cvxCrv).safeApprove(cvxcrvStaking, uint256(-1));

        IERC20(stakingToken).safeApprove(stakingProxy, 0);
        IERC20(stakingToken).safeApprove(stakingProxy, uint256(-1));
    }

    /* ========== VIEWS ========== */

    function _rewardPerToken(address _rewardsToken) internal view returns(uint256) {
        if (boostedSupply == 0) {
            return rewardData[_rewardsToken].rewardPerTokenStored;
        }
        return
        uint256(rewardData[_rewardsToken].rewardPerTokenStored).add(
            _lastTimeRewardApplicable(rewardData[_rewardsToken].periodFinish).sub(
                rewardData[_rewardsToken].lastUpdateTime).mul(
                rewardData[_rewardsToken].rewardRate).mul(1e18).div(rewardData[_rewardsToken].useBoost ? boostedSupply : lockedSupply)
        );
    }

    function _earned(
        address _user,
        address _rewardsToken,
        uint256 _balance
    ) internal view returns(uint256) {
        return _balance.mul(
            _rewardPerToken(_rewardsToken).sub(userRewardPerTokenPaid[_user][_rewardsToken])
        ).div(1e18).add(rewards[_user][_rewardsToken]);
    }

    function _lastTimeRewardApplicable(uint256 _finishTime) internal view returns(uint256){
        return Math.min(block.timestamp, _finishTime);
    }

    function lastTimeRewardApplicable(address _rewardsToken) public view returns(uint256) {
        return _lastTimeRewardApplicable(rewardData[_rewardsToken].periodFinish);
    }

    function rewardPerToken(address _rewardsToken) external view returns(uint256) {
        return _rewardPerToken(_rewardsToken);
    }

    function getRewardForDuration(address _rewardsToken) external view returns(uint256) {
        return uint256(rewardData[_rewardsToken].rewardRate).mul(rewardsDuration);
    }

    // Address and claimable amount of all reward tokens for the given account
    function claimableRewards(address _account) external view returns(EarnedData[] memory userRewards) {
        userRewards = new EarnedData[](rewardTokens.length);
        Balances storage userBalance = balances[_account];
        uint256 boostedBal = userBalance.boosted;
        for (uint256 i = 0; i < userRewards.length; i++) {
            address token = rewardTokens[i];
            userRewards[i].token = token;
            userRewards[i].amount = _earned(_account, token, rewardData[token].useBoost ? boostedBal : userBalance.locked);
        }
        return userRewards;
    }

    // Total BOOSTED balance of an account, including unlocked but not withdrawn tokens
    function rewardWeightOf(address _user) view external returns(uint256 amount) {
        return balances[_user].boosted;
    }

    // total token balance of an account, including unlocked but not withdrawn tokens
    function lockedBalanceOf(address _user) view external returns(uint256 amount) {
        return balances[_user].locked;
    }

    //BOOSTED balance of an account which only includes properly locked tokens as of the most recent eligible epoch
    function balanceOf(address _user) view external returns(uint256 amount) {
        LockedBalance[] storage locks = userLocks[_user];
        Balances storage userBalance = balances[_user];
        uint256 nextUnlockIndex = userBalance.nextUnlockIndex;

        //start with current boosted amount
        amount = balances[_user].boosted;

        uint256 locksLength = locks.length;
        //remove old records only (will be better gas-wise than adding up)
        for (uint i = nextUnlockIndex; i < locksLength; i++) {
            if (locks[i].unlockTime <= block.timestamp) {
                amount = amount.sub(locks[i].boosted);
            } else {
                //stop now as no futher checks are needed
                break;
            }
        }

        //also remove amount locked in the next epoch
        uint256 currentEpoch = block.timestamp.div(rewardsDuration).mul(rewardsDuration);
        if (locksLength > 0 && uint256(locks[locksLength - 1].unlockTime).sub(lockDuration) > currentEpoch) {
            amount = amount.sub(locks[locksLength - 1].boosted);
        }

        return amount;
    }

    //BOOSTED balance of an account which only includes properly locked tokens at the given epoch
    function balanceAtEpochOf(uint256 _epoch, address _user) view external returns(uint256 amount) {
        LockedBalance[] storage locks = userLocks[_user];

        //get timestamp of given epoch index
        uint256 epochTime = epochs[_epoch].date;
        //get timestamp of first non-inclusive epoch
        uint256 cutoffEpoch = epochTime.sub(lockDuration);

        //need to add up since the range could be in the middle somewhere
        //traverse inversely to make more current queries more gas efficient
        for (uint i = locks.length - 1; i + 1 != 0; i--) {
            uint256 lockEpoch = uint256(locks[i].unlockTime).sub(lockDuration);
            //lock epoch must be less or equal to the epoch we're basing from.
            if (lockEpoch <= epochTime) {
                if (lockEpoch > cutoffEpoch) {
                    amount = amount.add(locks[i].boosted);
                } else {
                    //stop now as no futher checks matter
                    break;
                }
            }
        }

        return amount;
    }

    //return currently locked but not active balance
    function pendingLockOf(address _user) view external returns(uint256 amount) {
        LockedBalance[] storage locks = userLocks[_user];

        uint256 locksLength = locks.length;

        //return amount if latest lock is in the future
        uint256 currentEpoch = block.timestamp.div(rewardsDuration).mul(rewardsDuration);
        if (locksLength > 0 && uint256(locks[locksLength - 1].unlockTime).sub(lockDuration) > currentEpoch) {
            return locks[locksLength - 1].boosted;
        }

        return 0;
    }

    function pendingLockAtEpochOf(uint256 _epoch, address _user) view external returns(uint256 amount) {
        LockedBalance[] storage locks = userLocks[_user];

        //get next epoch from the given epoch index
        uint256 nextEpoch = uint256(epochs[_epoch].date).add(rewardsDuration);

        //traverse inversely to make more current queries more gas efficient
        for (uint i = locks.length - 1; i + 1 != 0; i--) {
            uint256 lockEpoch = uint256(locks[i].unlockTime).sub(lockDuration);
            
            //return the next epoch balance
            if (lockEpoch == nextEpoch) {
                return locks[i].boosted;
            }else if(lockEpoch < nextEpoch){
                //no need to check anymore
                break;
            }
        }

        return 0;
    }

    //supply of all properly locked BOOSTED balances at most recent eligible epoch
    function totalSupply() view external returns(uint256 supply) {

        uint256 currentEpoch = block.timestamp.div(rewardsDuration).mul(rewardsDuration);
        uint256 cutoffEpoch = currentEpoch.sub(lockDuration);
        uint256 epochindex = epochs.length;

        //do not include next epoch's supply
        if ( uint256(epochs[epochindex - 1].date) > currentEpoch ) {
            epochindex--;
        }

        //traverse inversely to make more current queries more gas efficient
        for (uint i = epochindex - 1; i + 1 != 0; i--) {
            Epoch storage e = epochs[i];
            if (uint256(e.date) <= cutoffEpoch) {
                break;
            }
            supply = supply.add(e.supply);
        }

        return supply;
    }

    //supply of all properly locked BOOSTED balances at the given epoch
    function totalSupplyAtEpoch(uint256 _epoch) view external returns(uint256 supply) {

        uint256 epochStart = uint256(epochs[_epoch].date).div(rewardsDuration).mul(rewardsDuration);
        uint256 cutoffEpoch = epochStart.sub(lockDuration);

        //traverse inversely to make more current queries more gas efficient
        for (uint i = _epoch; i + 1 != 0; i--) {
            Epoch storage e = epochs[i];
            if (uint256(e.date) <= cutoffEpoch) {
                break;
            }
            supply = supply.add(epochs[i].supply);
        }

        return supply;
    }

    //find an epoch index based on timestamp
    function findEpochId(uint256 _time) view external returns(uint256 epoch) {
        uint256 max = epochs.length - 1;
        uint256 min = 0;

        //convert to start point
        _time = _time.div(rewardsDuration).mul(rewardsDuration);

        for (uint256 i = 0; i < 128; i++) {
            if (min >= max) break;

            uint256 mid = (min + max + 1) / 2;
            uint256 midEpochBlock = epochs[mid].date;
            if(midEpochBlock == _time){
                //found
                return mid;
            }else if (midEpochBlock < _time) {
                min = mid;
            } else{
                max = mid - 1;
            }
        }
        return min;
    }


    // Information on a user's locked balances
    function lockedBalances(
        address _user
    ) view external returns(
        uint256 total,
        uint256 unlockable,
        uint256 locked,
        LockedBalance[] memory lockData
    ) {
        LockedBalance[] storage locks = userLocks[_user];
        Balances storage userBalance = balances[_user];
        uint256 nextUnlockIndex = userBalance.nextUnlockIndex;
        uint256 idx;
        for (uint i = nextUnlockIndex; i < locks.length; i++) {
            if (locks[i].unlockTime > block.timestamp) {
                if (idx == 0) {
                    lockData = new LockedBalance[](locks.length - i);
                }
                lockData[idx] = locks[i];
                idx++;
                locked = locked.add(locks[i].amount);
            } else {
                unlockable = unlockable.add(locks[i].amount);
            }
        }
        return (userBalance.locked, unlockable, locked, lockData);
    }

    //number of epochs
    function epochCount() external view returns(uint256) {
        return epochs.length;
    }

    /* ========== MUTATIVE FUNCTIONS ========== */

    function checkpointEpoch() external {
        _checkpointEpoch();
    }

    //insert a new epoch if needed. fill in any gaps
    function _checkpointEpoch() internal {
        //create new epoch in the future where new non-active locks will lock to
        uint256 nextEpoch = block.timestamp.div(rewardsDuration).mul(rewardsDuration).add(rewardsDuration);
        uint256 epochindex = epochs.length;

        //first epoch add in constructor, no need to check 0 length

        //check to add
        if (epochs[epochindex - 1].date < nextEpoch) {
            //fill any epoch gaps
            while(epochs[epochs.length-1].date != nextEpoch){
                uint256 nextEpochDate = uint256(epochs[epochs.length-1].date).add(rewardsDuration);
                epochs.push(Epoch({
                    supply: 0,
                    date: uint32(nextEpochDate)
                }));
            }

            //update boost parameters on a new epoch
            if(boostRate != nextBoostRate){
                boostRate = nextBoostRate;
            }
            if(maximumBoostPayment != nextMaximumBoostPayment){
                maximumBoostPayment = nextMaximumBoostPayment;
            }
        }
    }

    // Locked tokens cannot be withdrawn for lockDuration and are eligible to receive stakingReward rewards
    function lock(address _account, uint256 _amount, uint256 _spendRatio) external nonReentrant updateReward(_account) {

        //pull tokens
        stakingToken.safeTransferFrom(msg.sender, address(this), _amount);

        //lock
        _lock(_account, _amount, _spendRatio, false);
    }

    //lock tokens
    function _lock(address _account, uint256 _amount, uint256 _spendRatio, bool _isRelock) internal {
        require(_amount > 0, "Cannot stake 0");
        require(_spendRatio <= maximumBoostPayment, "over max spend");
        require(!isShutdown, "shutdown");

        Balances storage bal = balances[_account];

        //must try check pointing epoch first
        _checkpointEpoch();

        //calc lock and boosted amount
        uint256 spendAmount = _amount.mul(_spendRatio).div(denominator);
        uint256 boostRatio = boostRate.mul(_spendRatio).div(maximumBoostPayment==0?1:maximumBoostPayment);
        uint112 lockAmount = _amount.sub(spendAmount).to112();
        uint112 boostedAmount = _amount.add(_amount.mul(boostRatio).div(denominator)).to112();

        //add user balances
        bal.locked = bal.locked.add(lockAmount);
        bal.boosted = bal.boosted.add(boostedAmount);

        //add to total supplies
        lockedSupply = lockedSupply.add(lockAmount);
        boostedSupply = boostedSupply.add(boostedAmount);

        //add user lock records or add to current
        uint256 lockEpoch = block.timestamp.div(rewardsDuration).mul(rewardsDuration);
        //if a fresh lock, add on an extra duration period
        if(!_isRelock){
            lockEpoch = lockEpoch.add(rewardsDuration);
        }
        uint256 unlockTime = lockEpoch.add(lockDuration);
        uint256 idx = userLocks[_account].length;

        //if the latest user lock is smaller than this lock, always just add new entry to the end of the list
        if (idx == 0 || userLocks[_account][idx - 1].unlockTime < unlockTime) {
            userLocks[_account].push(LockedBalance({
                amount: lockAmount,
                boosted: boostedAmount,
                unlockTime: uint32(unlockTime)
            }));
        } else {
            //else add to a current lock

            //if latest lock is further in the future, lower index
            //this can only happen if relocking an expired lock after creating a new lock
            if(userLocks[_account][idx - 1].unlockTime > unlockTime){
                idx--;
            }

            //if idx points to the epoch when same unlock time, update
            //(this is always true with a normal lock but maybe not with relock)
            if(userLocks[_account][idx - 1].unlockTime == unlockTime){
                LockedBalance storage userL = userLocks[_account][idx - 1];
                userL.amount = userL.amount.add(lockAmount);
                userL.boosted = userL.boosted.add(boostedAmount);
            }else{
                //can only enter here if a relock is made after a lock and there's no lock entry
                //for the current epoch.
                //ex a list of locks such as "[...][older][current*][next]" but without a "current" lock
                //length - 1 is the next epoch
                //length - 2 is a past epoch
                //thus need to insert an entry for current epoch at the 2nd to last entry
                //we will copy and insert the tail entry(next) and then overwrite length-2 entry

                //reset idx
                idx = userLocks[_account].length;

                //get current last item
                LockedBalance storage userL = userLocks[_account][idx - 1];

                //add a copy to end of list
                userLocks[_account].push(LockedBalance({
                    amount: userL.amount,
                    boosted: userL.boosted,
                    unlockTime: userL.unlockTime
                }));

                //insert current epoch lock entry by overwriting the entry at length-2
                userL.amount = lockAmount;
                userL.boosted = boostedAmount;
                userL.unlockTime = uint32(unlockTime);
            }
        }

        
        //update epoch supply, epoch checkpointed above so safe to add to latest
        uint256 eIndex = epochs.length - 1;
        //if relock, epoch should be current and not next, thus need to decrease index to length-2
        if(_isRelock){
            eIndex--;
        }
        Epoch storage e = epochs[eIndex];
        e.supply = e.supply.add(uint224(boostedAmount));

        //send boost payment
        if (spendAmount > 0) {
            stakingToken.safeTransfer(boostPayment, spendAmount);
        }

        //update staking, allow a bit of leeway for smaller deposits to reduce gas
        updateStakeRatio(stakeOffsetOnLock);

        emit Staked(_account, lockEpoch, _amount, lockAmount, boostedAmount);
    }

    // Withdraw all currently locked tokens where the unlock time has passed
    function _processExpiredLocks(address _account, bool _relock, uint256 _spendRatio, address _withdrawTo, address _rewardAddress, uint256 _checkDelay) internal updateReward(_account) {
        LockedBalance[] storage locks = userLocks[_account];
        Balances storage userBalance = balances[_account];
        uint112 locked;
        uint112 boostedAmount;
        uint256 length = locks.length;
        uint256 reward = 0;
        
        if (isShutdown || locks[length - 1].unlockTime <= block.timestamp.sub(_checkDelay)) {
            //if time is beyond last lock, can just bundle everything together
            locked = userBalance.locked;
            boostedAmount = userBalance.boosted;

            //dont delete, just set next index
            userBalance.nextUnlockIndex = length.to32();

            //check for kick reward
            //this wont have the exact reward rate that you would get if looped through
            //but this section is supposed to be for quick and easy low gas processing of all locks
            //we'll assume that if the reward was good enough someone would have processed at an earlier epoch
            if (_checkDelay > 0) {
                uint256 currentEpoch = block.timestamp.sub(_checkDelay).div(rewardsDuration).mul(rewardsDuration);
                uint256 epochsover = currentEpoch.sub(uint256(locks[length - 1].unlockTime)).div(rewardsDuration);
                uint256 rRate = MathUtil.min(kickRewardPerEpoch.mul(epochsover+1), denominator);
                reward = uint256(locks[length - 1].amount).mul(rRate).div(denominator);
            }
        } else {

            //use a processed index(nextUnlockIndex) to not loop as much
            //deleting does not change array length
            uint32 nextUnlockIndex = userBalance.nextUnlockIndex;
            for (uint i = nextUnlockIndex; i < length; i++) {
                //unlock time must be less or equal to time
                if (locks[i].unlockTime > block.timestamp.sub(_checkDelay)) break;

                //add to cumulative amounts
                locked = locked.add(locks[i].amount);
                boostedAmount = boostedAmount.add(locks[i].boosted);

                //check for kick reward
                //each epoch over due increases reward
                if (_checkDelay > 0) {
                    uint256 currentEpoch = block.timestamp.sub(_checkDelay).div(rewardsDuration).mul(rewardsDuration);
                    uint256 epochsover = currentEpoch.sub(uint256(locks[i].unlockTime)).div(rewardsDuration);
                    uint256 rRate = MathUtil.min(kickRewardPerEpoch.mul(epochsover+1), denominator);
                    reward = reward.add( uint256(locks[i].amount).mul(rRate).div(denominator));
                }
                //set next unlock index
                nextUnlockIndex++;
            }
            //update next unlock index
            userBalance.nextUnlockIndex = nextUnlockIndex;
        }
        require(locked > 0, "no exp locks");

        //update user balances and total supplies
        userBalance.locked = userBalance.locked.sub(locked);
        userBalance.boosted = userBalance.boosted.sub(boostedAmount);
        lockedSupply = lockedSupply.sub(locked);
        boostedSupply = boostedSupply.sub(boostedAmount);

        emit Withdrawn(_account, locked, _relock);

        //send process incentive
        if (reward > 0) {
            //if theres a reward(kicked), it will always be a withdraw only
            //preallocate enough cvx from stake contract to pay for both reward and withdraw
            allocateCVXForTransfer(uint256(locked));

            //reduce return amount by the kick reward
            locked = locked.sub(reward.to112());
            
            //transfer reward
            transferCVX(_rewardAddress, reward, false);

            emit KickReward(_rewardAddress, _account, reward);
        }else if(_spendRatio > 0){
            //preallocate enough cvx to transfer the boost cost
            allocateCVXForTransfer( uint256(locked).mul(_spendRatio).div(denominator) );
        }

        //relock or return to user
        if (_relock) {
            _lock(_withdrawTo, locked, _spendRatio, true);
        } else {
            transferCVX(_withdrawTo, locked, true);
        }
    }

    // withdraw expired locks to a different address
    function withdrawExpiredLocksTo(address _withdrawTo) external nonReentrant {
        _processExpiredLocks(msg.sender, false, 0, _withdrawTo, msg.sender, 0);
    }

    // Withdraw/relock all currently locked tokens where the unlock time has passed
    function processExpiredLocks(bool _relock) external nonReentrant {
        _processExpiredLocks(msg.sender, _relock, 0, msg.sender, msg.sender, 0);
    }

    function kickExpiredLocks(address _account) external nonReentrant {
        //allow kick after grace period of 'kickRewardEpochDelay'
        _processExpiredLocks(_account, false, 0, _account, msg.sender, rewardsDuration.mul(kickRewardEpochDelay));
    }

    //pull required amount of cvx from staking for an upcoming transfer
    function allocateCVXForTransfer(uint256 _amount) internal{
        uint256 balance = stakingToken.balanceOf(address(this));
        if (_amount > balance) {
            IStakingProxy(stakingProxy).withdraw(_amount.sub(balance));
        }
    }

    //transfer helper: pull enough from staking, transfer, updating staking ratio
    function transferCVX(address _account, uint256 _amount, bool _updateStake) internal {
        //allocate enough cvx from staking for the transfer
        allocateCVXForTransfer(_amount);
        //transfer
        stakingToken.safeTransfer(_account, _amount);

        //update staking
        if(_updateStake){
            updateStakeRatio(0);
        }
    }

    //calculate how much cvx should be staked. update if needed
    function updateStakeRatio(uint256 _offset) internal {
        if (isShutdown) return;

        //get balances
        uint256 local = stakingToken.balanceOf(address(this));
        uint256 staked = IStakingProxy(stakingProxy).getBalance();
        uint256 total = local.add(staked);
        
        if(total == 0) return;

        //current staked ratio
        uint256 ratio = staked.mul(denominator).div(total);
        //mean will be where we reset to if unbalanced
        uint256 mean = maximumStake.add(minimumStake).div(2);
        uint256 max = maximumStake.add(_offset);
        uint256 min = Math.min(minimumStake, minimumStake - _offset);
        if (ratio > max) {
            //remove
            uint256 remove = staked.sub(total.mul(mean).div(denominator));
            IStakingProxy(stakingProxy).withdraw(remove);
        } else if (ratio < min) {
            //add
            uint256 increase = total.mul(mean).div(denominator).sub(staked);
            stakingToken.safeTransfer(stakingProxy, increase);
            IStakingProxy(stakingProxy).stake();
        }
    }

    // Claim all pending rewards
    function getReward(address _account, bool _stake) public nonReentrant updateReward(_account) {
        for (uint i; i < rewardTokens.length; i++) {
            address _rewardsToken = rewardTokens[i];
            uint256 reward = rewards[_account][_rewardsToken];
            if (reward > 0) {
                rewards[_account][_rewardsToken] = 0;
                if (_rewardsToken == cvxCrv && _stake) {
                    IRewardStaking(cvxcrvStaking).stakeFor(_account, reward);
                } else {
                    IERC20(_rewardsToken).safeTransfer(_account, reward);
                }
                emit RewardPaid(_account, _rewardsToken, reward);
            }
        }
    }

    // claim all pending rewards
    function getReward(address _account) external{
        getReward(_account,false);
    }


    /* ========== RESTRICTED FUNCTIONS ========== */

    function _notifyReward(address _rewardsToken, uint256 _reward) internal {
        Reward storage rdata = rewardData[_rewardsToken];

        if (block.timestamp >= rdata.periodFinish) {
            rdata.rewardRate = _reward.div(rewardsDuration).to208();
        } else {
            uint256 remaining = uint256(rdata.periodFinish).sub(block.timestamp);
            uint256 leftover = remaining.mul(rdata.rewardRate);
            rdata.rewardRate = _reward.add(leftover).div(rewardsDuration).to208();
        }

        rdata.lastUpdateTime = block.timestamp.to40();
        rdata.periodFinish = block.timestamp.add(rewardsDuration).to40();
    }

    function notifyRewardAmount(address _rewardsToken, uint256 _reward) external updateReward(address(0)) {
        require(rewardDistributors[_rewardsToken][msg.sender]);
        require(_reward > 0, "No reward");

        _notifyReward(_rewardsToken, _reward);

        // handle the transfer of reward tokens via `transferFrom` to reduce the number
        // of transactions required and ensure correctness of the _reward amount
        IERC20(_rewardsToken).safeTransferFrom(msg.sender, address(this), _reward);
        
        emit RewardAdded(_rewardsToken, _reward);

        if(_rewardsToken == cvxCrv){
            //update staking ratio if main reward
            updateStakeRatio(0);
        }
    }

    // Added to support recovering LP Rewards from other systems such as BAL to be distributed to holders
    function recoverERC20(address _tokenAddress, uint256 _tokenAmount) external onlyOwner {
        require(_tokenAddress != address(stakingToken), "Cannot withdraw staking token");
        require(rewardData[_tokenAddress].lastUpdateTime == 0, "Cannot withdraw reward token");
        IERC20(_tokenAddress).safeTransfer(owner(), _tokenAmount);
        emit Recovered(_tokenAddress, _tokenAmount);
    }

    /* ========== MODIFIERS ========== */

    modifier updateReward(address _account) {
        {//stack too deep
            Balances storage userBalance = balances[_account];
            uint256 boostedBal = userBalance.boosted;
            for (uint i = 0; i < rewardTokens.length; i++) {
                address token = rewardTokens[i];
                rewardData[token].rewardPerTokenStored = _rewardPerToken(token).to208();
                rewardData[token].lastUpdateTime = _lastTimeRewardApplicable(rewardData[token].periodFinish).to40();
                if (_account != address(0)) {
                    //check if reward is boostable or not. use boosted or locked balance accordingly
                    rewards[_account][token] = _earned(_account, token, rewardData[token].useBoost ? boostedBal : userBalance.locked );
                    userRewardPerTokenPaid[_account][token] = rewardData[token].rewardPerTokenStored;
                }
            }
        }
        _;
    }

    /* ========== EVENTS ========== */
    event RewardAdded(address indexed _token, uint256 _reward);
    event Staked(address indexed _user, uint256 indexed _epoch, uint256 _paidAmount, uint256 _lockedAmount, uint256 _boostedAmount);
    event Withdrawn(address indexed _user, uint256 _amount, bool _relocked);
    event KickReward(address indexed _user, address indexed _kicked, uint256 _reward);
    event RewardPaid(address indexed _user, address indexed _rewardsToken, uint256 _reward);
    event Recovered(address _token, uint256 _amount);
}

// SPDX-License-Identifier: MIT
// File: contracts\Interfaces.sol

pragma solidity 0.6.12;


/**
 * @dev Standard math utilities missing in the Solidity language.
 */
library MathUtil {
    /**
     * @dev Returns the smallest of two numbers.
     */
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }
}

contract ReentrancyGuard {
    uint256 private _guardCounter;

    constructor () internal {
        _guardCounter = 1;
    }

    modifier nonReentrant() {
        _guardCounter += 1;
        uint256 localCounter = _guardCounter;
        _;
        require(localCounter == _guardCounter, "ReentrancyGuard: reentrant call");
    }
}

interface ICurveGauge {
    function deposit(uint256) external;
    function balanceOf(address) external view returns (uint256);
    function withdraw(uint256) external;
    function claim_rewards() external;
    function reward_tokens(uint256) external view returns(address);//v2
    function rewarded_token() external view returns(address);//v1
}

interface ICurveVoteEscrow {
    function create_lock(uint256, uint256) external;
    function increase_amount(uint256) external;
    function increase_unlock_time(uint256) external;
    function withdraw() external;
    function smart_wallet_checker() external view returns (address);
}

interface IWalletChecker {
    function check(address) external view returns (bool);
}

interface IVoting{
    function vote(uint256, bool, bool) external; //voteId, support, executeIfDecided
    function getVote(uint256) external view returns(bool,bool,uint64,uint64,uint64,uint64,uint256,uint256,uint256,bytes memory); 
    function vote_for_gauge_weights(address,uint256) external;
}

interface IMinter{
    function mint(address) external;
}

interface IRegistry{
    function get_registry() external view returns(address);
    function get_address(uint256 _id) external view returns(address);
    function gauge_controller() external view returns(address);
    function get_lp_token(address) external view returns(address);
    function get_gauges(address) external view returns(address[10] memory,uint128[10] memory);
}

interface IStaker{
    function deposit(address, address) external;
    function withdraw(address) external;
    function withdraw(address, address, uint256) external;
    function withdrawAll(address, address) external;
    function createLock(uint256, uint256) external;
    function increaseAmount(uint256) external;
    function increaseTime(uint256) external;
    function release() external;
    function claimCrv(address) external returns (uint256);
    function claimRewards(address) external;
    function claimFees(address,address) external;
    function setStashAccess(address, bool) external;
    function vote(uint256,address,bool) external;
    function voteGaugeWeight(address,uint256) external;
    function balanceOfPool(address) external view returns (uint256);
    function operator() external view returns (address);
    function execute(address _to, uint256 _value, bytes calldata _data) external returns (bool, bytes memory);
}

interface IRewards{
    function stake(address, uint256) external;
    function stakeFor(address, uint256) external;
    function withdraw(address, uint256) external;
    function exit(address) external;
    function getReward(address) external;
    function queueNewRewards(uint256) external;
    function notifyRewardAmount(uint256) external;
    function addExtraReward(address) external;
    function stakingToken() external returns (address);
}

interface IStash{
    function stashRewards() external returns (bool);
    function processStash() external returns (bool);
    function claimRewards() external returns (bool);
}

interface IFeeDistro{
    function claim() external;
    function token() external view returns(address);
}

interface ITokenMinter{
    function mint(address,uint256) external;
    function burn(address,uint256) external;
}

interface IDeposit{
    function isShutdown() external view returns(bool);
    function balanceOf(address _account) external view returns(uint256);
    function totalSupply() external view returns(uint256);
    function poolInfo(uint256) external view returns(address,address,address,address,address, bool);
    function rewardClaimed(uint256,address,uint256) external;
    function withdrawTo(uint256,uint256,address) external;
    function claimRewards(uint256,address) external returns(bool);
    function rewardArbitrator() external returns(address);
}

interface ICrvDeposit{
    function deposit(uint256, bool) external;
    function lockIncentive() external view returns(uint256);
}

interface IRewardFactory{
    function setAccess(address,bool) external;
    function CreateCrvRewards(uint256,address) external returns(address);
    function CreateTokenRewards(address,address,address) external returns(address);
    function activeRewardCount(address) external view returns(uint256);
    function addActiveReward(address,uint256) external returns(bool);
    function removeActiveReward(address,uint256) external returns(bool);
}

interface IStashFactory{
    function CreateStash(uint256,address,address,uint256) external returns(address);
}

interface ITokenFactory{
    function CreateDepositToken(address) external returns(address);
}

interface IPools{
    function addPool(address _lptoken, address _gauge, uint256 _stashVersion) external returns(bool);
    function shutdownPool(uint256 _pid) external returns(bool);
    function poolInfo(uint256) external view returns(address,address,address,address,address,bool);
    function poolLength() external view returns (uint256);
    function gaugeMap(address) external view returns(bool);
    function setPoolManager(address _poolM) external;
}

interface IVestedEscrow{
    function fund(address[] calldata _recipient, uint256[] calldata _amount) external returns(bool);
}

// File: @openzeppelin\contracts\math\SafeMath.sol

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b > a) return (false, 0);
        return (true, a - b);
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) return (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }

    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");
        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a, "SafeMath: subtraction overflow");
        return a - b;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) return 0;
        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");
        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: modulo by zero");
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        return a - b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a % b;
    }
}

// File: @openzeppelin\contracts\token\ERC20\IERC20.sol

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

// File: @openzeppelin\contracts\utils\Address.sol

pragma solidity >=0.6.2 <0.8.0;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{ value: amount }("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: value }(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data, string memory errorMessage) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// File: @openzeppelin\contracts\token\ERC20\SafeERC20.sol

pragma solidity >=0.6.0 <0.8.0;


/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using SafeMath for uint256;
    using Address for address;

    function safeTransfer(IERC20 token, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(IERC20 token, address spender, uint256 value) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).add(value);
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

// File: node_modules\@openzeppelin\contracts\utils\Context.sol

pragma solidity >=0.6.0 <0.8.0;

/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with GSN meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

// File: @openzeppelin\contracts\token\ERC20\ERC20.sol

pragma solidity >=0.6.0 <0.8.0;


/**
 * @dev Implementation of the {IERC20} interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using {_mint}.
 * For a generic mechanism see {ERC20PresetMinterPauser}.
 *
 * TIP: For a detailed writeup see our guide
 * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * We have followed general OpenZeppelin guidelines: functions revert instead
 * of returning `false` on failure. This behavior is nonetheless conventional
 * and does not conflict with the expectations of ERC20 applications.
 *
 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See {IERC20-approve}.
 */
contract ERC20 is Context, IERC20 {
    using SafeMath for uint256;

    mapping (address => uint256) private _balances;

    mapping (address => mapping (address => uint256)) private _allowances;

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;
    uint8 private _decimals;

    /**
     * @dev Sets the values for {name} and {symbol}, initializes {decimals} with
     * a default value of 18.
     *
     * To select a different value for {decimals}, use {_setupDecimals}.
     *
     * All three of these values are immutable: they can only be set once during
     * construction.
     */
    constructor (string memory name_, string memory symbol_) public {
        _name = name_;
        _symbol = symbol_;
        _decimals = 18;
    }

    /**
     * @dev Returns the name of the token.
     */
    function name() public view virtual returns (string memory) {
        return _name;
    }

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view virtual returns (string memory) {
        return _symbol;
    }

    /**
     * @dev Returns the number of decimals used to get its user representation.
     * For example, if `decimals` equals `2`, a balance of `505` tokens should
     * be displayed to a user as `5,05` (`505 / 10 ** 2`).
     *
     * Tokens usually opt for a value of 18, imitating the relationship between
     * Ether and Wei. This is the value {ERC20} uses, unless {_setupDecimals} is
     * called.
     *
     * NOTE: This information is only used for _display_ purposes: it in
     * no way affects any of the arithmetic of the contract, including
     * {IERC20-balanceOf} and {IERC20-transfer}.
     */
    function decimals() public view virtual returns (uint8) {
        return _decimals;
    }

    /**
     * @dev See {IERC20-totalSupply}.
     */
    function totalSupply() public view virtual override returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view virtual override returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See {IERC20-transfer}.
     *
     * Requirements:
     *
     * - `recipient` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }

    /**
     * @dev See {IERC20-allowance}.
     */
    function allowance(address owner, address spender) public view virtual override returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See {IERC20-approve}.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        _approve(_msgSender(), spender, amount);
        return true;
    }

    /**
     * @dev See {IERC20-transferFrom}.
     *
     * Emits an {Approval} event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of {ERC20}.
     *
     * Requirements:
     *
     * - `sender` and `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     * - the caller must have allowance for ``sender``'s tokens of at least
     * `amount`.
     */
    function transferFrom(address sender, address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(sender, recipient, amount);
        _approve(sender, _msgSender(), _allowances[sender][_msgSender()].sub(amount, "ERC20: transfer amount exceeds allowance"));
        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].add(addedValue));
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].sub(subtractedValue, "ERC20: decreased allowance below zero"));
        return true;
    }

    /**
     * @dev Moves tokens `amount` from `sender` to `recipient`.
     *
     * This is internal function is equivalent to {transfer}, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a {Transfer} event.
     *
     * Requirements:
     *
     * - `sender` cannot be the zero address.
     * - `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     */
    function _transfer(address sender, address recipient, uint256 amount) internal virtual {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        _beforeTokenTransfer(sender, recipient, amount);

        _balances[sender] = _balances[sender].sub(amount, "ERC20: transfer amount exceeds balance");
        _balances[recipient] = _balances[recipient].add(amount);
        emit Transfer(sender, recipient, amount);
    }

    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a {Transfer} event with `from` set to the zero address.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     */
    function _mint(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: mint to the zero address");

        _beforeTokenTransfer(address(0), account, amount);

        _totalSupply = _totalSupply.add(amount);
        _balances[account] = _balances[account].add(amount);
        emit Transfer(address(0), account, amount);
    }

    /**
     * @dev Destroys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a {Transfer} event with `to` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    function _burn(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: burn from the zero address");

        _beforeTokenTransfer(account, address(0), amount);

        _balances[account] = _balances[account].sub(amount, "ERC20: burn amount exceeds balance");
        _totalSupply = _totalSupply.sub(amount);
        emit Transfer(account, address(0), amount);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
     *
     * This internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(address owner, address spender, uint256 amount) internal virtual {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    /**
     * @dev Sets {decimals} to a value other than the default one of 18.
     *
     * WARNING: This function should only be called from the constructor. Most
     * applications that interact with token contracts will not expect
     * {decimals} to ever change, and may work incorrectly if it does.
     */
    function _setupDecimals(uint8 decimals_) internal virtual {
        _decimals = decimals_;
    }

    /**
     * @dev Hook that is called before any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * will be to transferred to `to`.
     * - when `from` is zero, `amount` tokens will be minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(address from, address to, uint256 amount) internal virtual { }
}

// File: contracts\cCrv.sol

pragma solidity 0.6.12;



contract cvxCrvToken is ERC20 {
    using SafeERC20 for IERC20;
    using Address for address;
    using SafeMath for uint256;

    address public operator;

    constructor()
        public
        ERC20(
            "Convex CRV",
            "cvxCRV"
        )
    {
        operator = msg.sender;
    }

   function setOperator(address _operator) external {
        require(msg.sender == operator, "!auth");
        operator = _operator;
    }

    
    function mint(address _to, uint256 _amount) external {
        require(msg.sender == operator, "!authorized");
        
        _mint(_to, _amount);
    }

    function burn(address _from, uint256 _amount) external {
        require(msg.sender == operator, "!authorized");
        
        _burn(_from, _amount);
    }

}

// SPDX-License-Identifier: MIT
pragma solidity 0.8.10;
import '@openzeppelin/contracts/token/ERC20/ERC20.sol';
contract cvxFxsToken is ERC20 {
    address public operator;
    constructor()
        ERC20(
            "Convex FXS",
            "cvxFXS"
        )
    {
        operator = msg.sender;
    }
   function setOperator(address _operator) external {
        require(msg.sender == operator, "!auth");
        operator = _operator;
    }
    
    function mint(address _to, uint256 _amount) external {
        require(msg.sender == operator, "!authorized");
        
        _mint(_to, _amount);
    }
    function burn(address _from, uint256 _amount) external {
        require(msg.sender == operator, "!authorized");
        
        _burn(_from, _amount);
    }
}// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }
    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "../IERC20.sol";
/**
 * @dev Interface for the optional metadata functions from the ERC20 standard.
 *
 * _Available since v4.1._
 */
interface IERC20Metadata is IERC20 {
    /**
     * @dev Returns the name of the token.
     */
    function name() external view returns (string memory);
    /**
     * @dev Returns the symbol of the token.
     */
    function symbol() external view returns (string memory);
    /**
     * @dev Returns the decimals places of the token.
     */
    function decimals() external view returns (uint8);
}
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);
    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);
    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);
    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);
    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);
    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) external returns (bool);
    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);
    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "./IERC20.sol";
import "./extensions/IERC20Metadata.sol";
import "../../utils/Context.sol";
/**
 * @dev Implementation of the {IERC20} interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using {_mint}.
 * For a generic mechanism see {ERC20PresetMinterPauser}.
 *
 * TIP: For a detailed writeup see our guide
 * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * We have followed general OpenZeppelin Contracts guidelines: functions revert
 * instead returning `false` on failure. This behavior is nonetheless
 * conventional and does not conflict with the expectations of ERC20
 * applications.
 *
 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See {IERC20-approve}.
 */
contract ERC20 is Context, IERC20, IERC20Metadata {
    mapping(address => uint256) private _balances;
    mapping(address => mapping(address => uint256)) private _allowances;
    uint256 private _totalSupply;
    string private _name;
    string private _symbol;
    /**
     * @dev Sets the values for {name} and {symbol}.
     *
     * The default value of {decimals} is 18. To select a different value for
     * {decimals} you should overload it.
     *
     * All two of these values are immutable: they can only be set once during
     * construction.
     */
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }
    /**
     * @dev Returns the name of the token.
     */
    function name() public view virtual override returns (string memory) {
        return _name;
    }
    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }
    /**
     * @dev Returns the number of decimals used to get its user representation.
     * For example, if `decimals` equals `2`, a balance of `505` tokens should
     * be displayed to a user as `5.05` (`505 / 10 ** 2`).
     *
     * Tokens usually opt for a value of 18, imitating the relationship between
     * Ether and Wei. This is the value {ERC20} uses, unless this function is
     * overridden;
     *
     * NOTE: This information is only used for _display_ purposes: it in
     * no way affects any of the arithmetic of the contract, including
     * {IERC20-balanceOf} and {IERC20-transfer}.
     */
    function decimals() public view virtual override returns (uint8) {
        return 18;
    }
    /**
     * @dev See {IERC20-totalSupply}.
     */
    function totalSupply() public view virtual override returns (uint256) {
        return _totalSupply;
    }
    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view virtual override returns (uint256) {
        return _balances[account];
    }
    /**
     * @dev See {IERC20-transfer}.
     *
     * Requirements:
     *
     * - `recipient` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }
    /**
     * @dev See {IERC20-allowance}.
     */
    function allowance(address owner, address spender) public view virtual override returns (uint256) {
        return _allowances[owner][spender];
    }
    /**
     * @dev See {IERC20-approve}.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        _approve(_msgSender(), spender, amount);
        return true;
    }
    /**
     * @dev See {IERC20-transferFrom}.
     *
     * Emits an {Approval} event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of {ERC20}.
     *
     * Requirements:
     *
     * - `sender` and `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     * - the caller must have allowance for ``sender``'s tokens of at least
     * `amount`.
     */
    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) public virtual override returns (bool) {
        _transfer(sender, recipient, amount);
        uint256 currentAllowance = _allowances[sender][_msgSender()];
        require(currentAllowance >= amount, "ERC20: transfer amount exceeds allowance");
        unchecked {
            _approve(sender, _msgSender(), currentAllowance - amount);
        }
        return true;
    }
    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender] + addedValue);
        return true;
    }
    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
        uint256 currentAllowance = _allowances[_msgSender()][spender];
        require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
        unchecked {
            _approve(_msgSender(), spender, currentAllowance - subtractedValue);
        }
        return true;
    }
    /**
     * @dev Moves `amount` of tokens from `sender` to `recipient`.
     *
     * This internal function is equivalent to {transfer}, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a {Transfer} event.
     *
     * Requirements:
     *
     * - `sender` cannot be the zero address.
     * - `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     */
    function _transfer(
        address sender,
        address recipient,
        uint256 amount
    ) internal virtual {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");
        _beforeTokenTransfer(sender, recipient, amount);
        uint256 senderBalance = _balances[sender];
        require(senderBalance >= amount, "ERC20: transfer amount exceeds balance");
        unchecked {
            _balances[sender] = senderBalance - amount;
        }
        _balances[recipient] += amount;
        emit Transfer(sender, recipient, amount);
        _afterTokenTransfer(sender, recipient, amount);
    }
    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a {Transfer} event with `from` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     */
    function _mint(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: mint to the zero address");
        _beforeTokenTransfer(address(0), account, amount);
        _totalSupply += amount;
        _balances[account] += amount;
        emit Transfer(address(0), account, amount);
        _afterTokenTransfer(address(0), account, amount);
    }
    /**
     * @dev Destroys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a {Transfer} event with `to` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    function _burn(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: burn from the zero address");
        _beforeTokenTransfer(account, address(0), amount);
        uint256 accountBalance = _balances[account];
        require(accountBalance >= amount, "ERC20: burn amount exceeds balance");
        unchecked {
            _balances[account] = accountBalance - amount;
        }
        _totalSupply -= amount;
        emit Transfer(account, address(0), amount);
        _afterTokenTransfer(account, address(0), amount);
    }
    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
     *
     * This internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(
        address owner,
        address spender,
        uint256 amount
    ) internal virtual {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");
        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }
    /**
     * @dev Hook that is called before any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * will be transferred to `to`.
     * - when `from` is zero, `amount` tokens will be minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}
    /**
     * @dev Hook that is called after any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * has been transferred to `to`.
     * - when `from` is zero, `amount` tokens have been minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens have been burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _afterTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}
}

# @version 0.2.4
"""
@title Curve DAO Token
@author Curve Finance
@license MIT
@notice ERC20 with piecewise-linear mining supply.
@dev Based on the ERC-20 token standard as defined at
     https://eips.ethereum.org/EIPS/eip-20
"""

from vyper.interfaces import ERC20

implements: ERC20


event Transfer:
    _from: indexed(address)
    _to: indexed(address)
    _value: uint256

event Approval:
    _owner: indexed(address)
    _spender: indexed(address)
    _value: uint256

event UpdateMiningParameters:
    time: uint256
    rate: uint256
    supply: uint256

event SetMinter:
    minter: address

event SetAdmin:
    admin: address


name: public(String[64])
symbol: public(String[32])
decimals: public(uint256)

balanceOf: public(HashMap[address, uint256])
allowances: HashMap[address, HashMap[address, uint256]]
total_supply: uint256

minter: public(address)
admin: public(address)

# General constants
YEAR: constant(uint256) = 86400 * 365

# Allocation:
# =========
# * shareholders - 30%
# * emplyees - 3%
# * DAO-controlled reserve - 5%
# * Early users - 5%
# == 43% ==
# left for inflation: 57%

# Supply parameters
INITIAL_SUPPLY: constant(uint256) = 1_303_030_303
INITIAL_RATE: constant(uint256) = 274_815_283 * 10 ** 18 / YEAR  # leading to 43% premine
RATE_REDUCTION_TIME: constant(uint256) = YEAR
RATE_REDUCTION_COEFFICIENT: constant(uint256) = 1189207115002721024  # 2 ** (1/4) * 1e18
RATE_DENOMINATOR: constant(uint256) = 10 ** 18
INFLATION_DELAY: constant(uint256) = 86400

# Supply variables
mining_epoch: public(int128)
start_epoch_time: public(uint256)
rate: public(uint256)

start_epoch_supply: uint256


@external
def __init__(_name: String[64], _symbol: String[32], _decimals: uint256):
    """
    @notice Contract constructor
    @param _name Token full name
    @param _symbol Token symbol
    @param _decimals Number of decimals for token
    """
    init_supply: uint256 = INITIAL_SUPPLY * 10 ** _decimals
    self.name = _name
    self.symbol = _symbol
    self.decimals = _decimals
    self.balanceOf[msg.sender] = init_supply
    self.total_supply = init_supply
    self.admin = msg.sender
    log Transfer(ZERO_ADDRESS, msg.sender, init_supply)

    self.start_epoch_time = block.timestamp + INFLATION_DELAY - RATE_REDUCTION_TIME
    self.mining_epoch = -1
    self.rate = 0
    self.start_epoch_supply = init_supply


@internal
def _update_mining_parameters():
    """
    @dev Update mining rate and supply at the start of the epoch
         Any modifying mining call must also call this
    """
    _rate: uint256 = self.rate
    _start_epoch_supply: uint256 = self.start_epoch_supply

    self.start_epoch_time += RATE_REDUCTION_TIME
    self.mining_epoch += 1

    if _rate == 0:
        _rate = INITIAL_RATE
    else:
        _start_epoch_supply += _rate * RATE_REDUCTION_TIME
        self.start_epoch_supply = _start_epoch_supply
        _rate = _rate * RATE_DENOMINATOR / RATE_REDUCTION_COEFFICIENT

    self.rate = _rate

    log UpdateMiningParameters(block.timestamp, _rate, _start_epoch_supply)


@external
def update_mining_parameters():
    """
    @notice Update mining rate and supply at the start of the epoch
    @dev Callable by any address, but only once per epoch
         Total supply becomes slightly larger if this function is called late
    """
    assert block.timestamp >= self.start_epoch_time + RATE_REDUCTION_TIME  # dev: too soon!
    self._update_mining_parameters()


@external
def start_epoch_time_write() -> uint256:
    """
    @notice Get timestamp of the current mining epoch start
            while simultaneously updating mining parameters
    @return Timestamp of the epoch
    """
    _start_epoch_time: uint256 = self.start_epoch_time
    if block.timestamp >= _start_epoch_time + RATE_REDUCTION_TIME:
        self._update_mining_parameters()
        return self.start_epoch_time
    else:
        return _start_epoch_time


@external
def future_epoch_time_write() -> uint256:
    """
    @notice Get timestamp of the next mining epoch start
            while simultaneously updating mining parameters
    @return Timestamp of the next epoch
    """
    _start_epoch_time: uint256 = self.start_epoch_time
    if block.timestamp >= _start_epoch_time + RATE_REDUCTION_TIME:
        self._update_mining_parameters()
        return self.start_epoch_time + RATE_REDUCTION_TIME
    else:
        return _start_epoch_time + RATE_REDUCTION_TIME


@internal
@view
def _available_supply() -> uint256:
    return self.start_epoch_supply + (block.timestamp - self.start_epoch_time) * self.rate


@external
@view
def available_supply() -> uint256:
    """
    @notice Current number of tokens in existence (claimed or unclaimed)
    """
    return self._available_supply()


@external
@view
def mintable_in_timeframe(start: uint256, end: uint256) -> uint256:
    """
    @notice How much supply is mintable from start timestamp till end timestamp
    @param start Start of the time interval (timestamp)
    @param end End of the time interval (timestamp)
    @return Tokens mintable from `start` till `end`
    """
    assert start <= end  # dev: start > end
    to_mint: uint256 = 0
    current_epoch_time: uint256 = self.start_epoch_time
    current_rate: uint256 = self.rate

    # Special case if end is in future (not yet minted) epoch
    if end > current_epoch_time + RATE_REDUCTION_TIME:
        current_epoch_time += RATE_REDUCTION_TIME
        current_rate = current_rate * RATE_DENOMINATOR / RATE_REDUCTION_COEFFICIENT

    assert end <= current_epoch_time + RATE_REDUCTION_TIME  # dev: too far in future

    for i in range(999):  # Curve will not work in 1000 years. Darn!
        if end >= current_epoch_time:
            current_end: uint256 = end
            if current_end > current_epoch_time + RATE_REDUCTION_TIME:
                current_end = current_epoch_time + RATE_REDUCTION_TIME

            current_start: uint256 = start
            if current_start >= current_epoch_time + RATE_REDUCTION_TIME:
                break  # We should never get here but what if...
            elif current_start < current_epoch_time:
                current_start = current_epoch_time

            to_mint += current_rate * (current_end - current_start)

            if start >= current_epoch_time:
                break

        current_epoch_time -= RATE_REDUCTION_TIME
        current_rate = current_rate * RATE_REDUCTION_COEFFICIENT / RATE_DENOMINATOR  # double-division with rounding made rate a bit less => good
        assert current_rate <= INITIAL_RATE  # This should never happen

    return to_mint


@external
def set_minter(_minter: address):
    """
    @notice Set the minter address
    @dev Only callable once, when minter has not yet been set
    @param _minter Address of the minter
    """
    assert msg.sender == self.admin  # dev: admin only
    assert self.minter == ZERO_ADDRESS  # dev: can set the minter only once, at creation
    self.minter = _minter
    log SetMinter(_minter)


@external
def set_admin(_admin: address):
    """
    @notice Set the new admin.
    @dev After all is set up, admin only can change the token name
    @param _admin New admin address
    """
    assert msg.sender == self.admin  # dev: admin only
    self.admin = _admin
    log SetAdmin(_admin)


@external
@view
def totalSupply() -> uint256:
    """
    @notice Total number of tokens in existence.
    """
    return self.total_supply


@external
@view
def allowance(_owner : address, _spender : address) -> uint256:
    """
    @notice Check the amount of tokens that an owner allowed to a spender
    @param _owner The address which owns the funds
    @param _spender The address which will spend the funds
    @return uint256 specifying the amount of tokens still available for the spender
    """
    return self.allowances[_owner][_spender]


@external
def transfer(_to : address, _value : uint256) -> bool:
    """
    @notice Transfer `_value` tokens from `msg.sender` to `_to`
    @dev Vyper does not allow underflows, so the subtraction in
         this function will revert on an insufficient balance
    @param _to The address to transfer to
    @param _value The amount to be transferred
    @return bool success
    """
    assert _to != ZERO_ADDRESS  # dev: transfers to 0x0 are not allowed
    self.balanceOf[msg.sender] -= _value
    self.balanceOf[_to] += _value
    log Transfer(msg.sender, _to, _value)
    return True


@external
def transferFrom(_from : address, _to : address, _value : uint256) -> bool:
    """
     @notice Transfer `_value` tokens from `_from` to `_to`
     @param _from address The address which you want to send tokens from
     @param _to address The address which you want to transfer to
     @param _value uint256 the amount of tokens to be transferred
     @return bool success
    """
    assert _to != ZERO_ADDRESS  # dev: transfers to 0x0 are not allowed
    # NOTE: vyper does not allow underflows
    #       so the following subtraction would revert on insufficient balance
    self.balanceOf[_from] -= _value
    self.balanceOf[_to] += _value
    self.allowances[_from][msg.sender] -= _value
    log Transfer(_from, _to, _value)
    return True


@external
def approve(_spender : address, _value : uint256) -> bool:
    """
    @notice Approve `_spender` to transfer `_value` tokens on behalf of `msg.sender`
    @dev Approval may only be from zero -> nonzero or from nonzero -> zero in order
        to mitigate the potential race condition described here:
        https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
    @param _spender The address which will spend the funds
    @param _value The amount of tokens to be spent
    @return bool success
    """
    assert _value == 0 or self.allowances[msg.sender][_spender] == 0
    self.allowances[msg.sender][_spender] = _value
    log Approval(msg.sender, _spender, _value)
    return True


@external
def mint(_to: address, _value: uint256) -> bool:
    """
    @notice Mint `_value` tokens and assign them to `_to`
    @dev Emits a Transfer event originating from 0x00
    @param _to The account that will receive the created tokens
    @param _value The amount that will be created
    @return bool success
    """
    assert msg.sender == self.minter  # dev: minter only
    assert _to != ZERO_ADDRESS  # dev: zero address

    if block.timestamp >= self.start_epoch_time + RATE_REDUCTION_TIME:
        self._update_mining_parameters()

    _total_supply: uint256 = self.total_supply + _value
    assert _total_supply <= self._available_supply()  # dev: exceeds allowable mint amount
    self.total_supply = _total_supply

    self.balanceOf[_to] += _value
    log Transfer(ZERO_ADDRESS, _to, _value)

    return True


@external
def burn(_value: uint256) -> bool:
    """
    @notice Burn `_value` tokens belonging to `msg.sender`
    @dev Emits a Transfer event with a destination of 0x00
    @param _value The amount that will be burned
    @return bool success
    """
    self.balanceOf[msg.sender] -= _value
    self.total_supply -= _value

    log Transfer(msg.sender, ZERO_ADDRESS, _value)
    return True


@external
def set_name(_name: String[64], _symbol: String[32]):
    """
    @notice Change the token name and symbol to `_name` and `_symbol`
    @dev Only callable by the admin account
    @param _name New token name
    @param _symbol New token symbol
    """
    assert msg.sender == self.admin, "Only admin is allowed to change name"
    self.name = _name
    self.symbol = _symbol

// SPDX-License-Identifier: MIT


// File: contracts\Interfaces.sol
pragma solidity 0.6.12;

/**
 * @dev Standard math utilities missing in the Solidity language.
 */
library MathUtil {
    /**
     * @dev Returns the smallest of two numbers.
     */
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }
}

contract ReentrancyGuard {
    uint256 private _guardCounter;

    constructor () internal {
        _guardCounter = 1;
    }

    modifier nonReentrant() {
        _guardCounter += 1;
        uint256 localCounter = _guardCounter;
        _;
        require(localCounter == _guardCounter, "ReentrancyGuard: reentrant call");
    }
}

interface ICurveGauge {
    function deposit(uint256) external;
    function balanceOf(address) external view returns (uint256);
    function withdraw(uint256) external;
    function claim_rewards() external;
    function reward_tokens(uint256) external view returns(address);//v2
    function rewarded_token() external view returns(address);//v1
}

interface ICurveVoteEscrow {
    function create_lock(uint256, uint256) external;
    function increase_amount(uint256) external;
    function increase_unlock_time(uint256) external;
    function withdraw() external;
    function smart_wallet_checker() external view returns (address);
}

interface IWalletChecker {
    function check(address) external view returns (bool);
}

interface IVoting{
    function vote(uint256, bool, bool) external; //voteId, support, executeIfDecided
    function getVote(uint256) external view returns(bool,bool,uint64,uint64,uint64,uint64,uint256,uint256,uint256,bytes memory); 
    function vote_for_gauge_weights(address,uint256) external;
}

interface IMinter{
    function mint(address) external;
}

interface IRegistry{
    function get_registry() external view returns(address);
    function get_address(uint256 _id) external view returns(address);
    function gauge_controller() external view returns(address);
    function get_lp_token(address) external view returns(address);
    function get_gauges(address) external view returns(address[10] memory,uint128[10] memory);
}

interface IStaker{
    function deposit(address, address) external;
    function withdraw(address) external;
    function withdraw(address, address, uint256) external;
    function withdrawAll(address, address) external;
    function createLock(uint256, uint256) external;
    function increaseAmount(uint256) external;
    function increaseTime(uint256) external;
    function release() external;
    function claimCrv(address) external returns (uint256);
    function claimRewards(address) external;
    function claimFees(address,address) external;
    function setStashAccess(address, bool) external;
    function vote(uint256,address,bool) external;
    function voteGaugeWeight(address,uint256) external;
    function balanceOfPool(address) external view returns (uint256);
    function operator() external view returns (address);
    function execute(address _to, uint256 _value, bytes calldata _data) external returns (bool, bytes memory);
}

interface IRewards{
    function stake(address, uint256) external;
    function stakeFor(address, uint256) external;
    function withdraw(address, uint256) external;
    function exit(address) external;
    function getReward(address) external;
    function queueNewRewards(uint256) external;
    function notifyRewardAmount(uint256) external;
    function addExtraReward(address) external;
    function stakingToken() external returns (address);
}

interface IStash{
    function stashRewards() external returns (bool);
    function processStash() external returns (bool);
    function claimRewards() external returns (bool);
}

interface IFeeDistro{
    function claim() external;
    function token() external view returns(address);
}

interface ITokenMinter{
    function mint(address,uint256) external;
    function burn(address,uint256) external;
}

interface IDeposit{
    function isShutdown() external view returns(bool);
    function balanceOf(address _account) external view returns(uint256);
    function totalSupply() external view returns(uint256);
    function poolInfo(uint256) external view returns(address,address,address,address,address, bool);
    function rewardClaimed(uint256,address,uint256) external;
    function withdrawTo(uint256,uint256,address) external;
    function claimRewards(uint256,address) external returns(bool);
    function rewardArbitrator() external returns(address);
}

interface ICrvDeposit{
    function deposit(uint256, bool) external;
    function lockIncentive() external view returns(uint256);
}

interface IRewardFactory{
    function setAccess(address,bool) external;
    function CreateCrvRewards(uint256,address) external returns(address);
    function CreateTokenRewards(address,address,address) external returns(address);
    function activeRewardCount(address) external view returns(uint256);
    function addActiveReward(address,uint256) external returns(bool);
    function removeActiveReward(address,uint256) external returns(bool);
}

interface IStashFactory{
    function CreateStash(uint256,address,address,uint256) external returns(address);
}

interface ITokenFactory{
    function CreateDepositToken(address) external returns(address);
}

interface IPools{
    function addPool(address _lptoken, address _gauge, uint256 _stashVersion) external returns(bool);
    function shutdownPool(uint256 _pid) external returns(bool);
    function poolInfo(uint256) external view returns(address,address,address,address,address,bool);
    function poolLength() external view returns (uint256);
    function gaugeMap(address) external view returns(bool);
    function setPoolManager(address _poolM) external;
}

interface IVestedEscrow{
    function fund(address[] calldata _recipient, uint256[] calldata _amount) external returns(bool);
}

// File: @openzeppelin\contracts\math\SafeMath.sol

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b > a) return (false, 0);
        return (true, a - b);
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) return (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }

    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");
        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a, "SafeMath: subtraction overflow");
        return a - b;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) return 0;
        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");
        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: modulo by zero");
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        return a - b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a % b;
    }
}

// File: @openzeppelin\contracts\token\ERC20\IERC20.sol


pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

// File: @openzeppelin\contracts\utils\Address.sol

pragma solidity >=0.6.2 <0.8.0;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{ value: amount }("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: value }(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data, string memory errorMessage) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// File: @openzeppelin\contracts\token\ERC20\SafeERC20.sol

pragma solidity >=0.6.0 <0.8.0;


/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using SafeMath for uint256;
    using Address for address;

    function safeTransfer(IERC20 token, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(IERC20 token, address spender, uint256 value) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).add(value);
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

// File: node_modules\@openzeppelin\contracts\utils\Context.sol

pragma solidity >=0.6.0 <0.8.0;

/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with GSN meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

// File: @openzeppelin\contracts\token\ERC20\ERC20.sol

pragma solidity >=0.6.0 <0.8.0;


/**
 * @dev Implementation of the {IERC20} interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using {_mint}.
 * For a generic mechanism see {ERC20PresetMinterPauser}.
 *
 * TIP: For a detailed writeup see our guide
 * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * We have followed general OpenZeppelin guidelines: functions revert instead
 * of returning `false` on failure. This behavior is nonetheless conventional
 * and does not conflict with the expectations of ERC20 applications.
 *
 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See {IERC20-approve}.
 */
contract ERC20 is Context, IERC20 {
    using SafeMath for uint256;

    mapping (address => uint256) private _balances;

    mapping (address => mapping (address => uint256)) private _allowances;

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;
    uint8 private _decimals;

    /**
     * @dev Sets the values for {name} and {symbol}, initializes {decimals} with
     * a default value of 18.
     *
     * To select a different value for {decimals}, use {_setupDecimals}.
     *
     * All three of these values are immutable: they can only be set once during
     * construction.
     */
    constructor (string memory name_, string memory symbol_) public {
        _name = name_;
        _symbol = symbol_;
        _decimals = 18;
    }

    /**
     * @dev Returns the name of the token.
     */
    function name() public view virtual returns (string memory) {
        return _name;
    }

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view virtual returns (string memory) {
        return _symbol;
    }

    /**
     * @dev Returns the number of decimals used to get its user representation.
     * For example, if `decimals` equals `2`, a balance of `505` tokens should
     * be displayed to a user as `5,05` (`505 / 10 ** 2`).
     *
     * Tokens usually opt for a value of 18, imitating the relationship between
     * Ether and Wei. This is the value {ERC20} uses, unless {_setupDecimals} is
     * called.
     *
     * NOTE: This information is only used for _display_ purposes: it in
     * no way affects any of the arithmetic of the contract, including
     * {IERC20-balanceOf} and {IERC20-transfer}.
     */
    function decimals() public view virtual returns (uint8) {
        return _decimals;
    }

    /**
     * @dev See {IERC20-totalSupply}.
     */
    function totalSupply() public view virtual override returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view virtual override returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See {IERC20-transfer}.
     *
     * Requirements:
     *
     * - `recipient` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }

    /**
     * @dev See {IERC20-allowance}.
     */
    function allowance(address owner, address spender) public view virtual override returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See {IERC20-approve}.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        _approve(_msgSender(), spender, amount);
        return true;
    }

    /**
     * @dev See {IERC20-transferFrom}.
     *
     * Emits an {Approval} event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of {ERC20}.
     *
     * Requirements:
     *
     * - `sender` and `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     * - the caller must have allowance for ``sender``'s tokens of at least
     * `amount`.
     */
    function transferFrom(address sender, address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(sender, recipient, amount);
        _approve(sender, _msgSender(), _allowances[sender][_msgSender()].sub(amount, "ERC20: transfer amount exceeds allowance"));
        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].add(addedValue));
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].sub(subtractedValue, "ERC20: decreased allowance below zero"));
        return true;
    }

    /**
     * @dev Moves tokens `amount` from `sender` to `recipient`.
     *
     * This is internal function is equivalent to {transfer}, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a {Transfer} event.
     *
     * Requirements:
     *
     * - `sender` cannot be the zero address.
     * - `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     */
    function _transfer(address sender, address recipient, uint256 amount) internal virtual {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        _beforeTokenTransfer(sender, recipient, amount);

        _balances[sender] = _balances[sender].sub(amount, "ERC20: transfer amount exceeds balance");
        _balances[recipient] = _balances[recipient].add(amount);
        emit Transfer(sender, recipient, amount);
    }

    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a {Transfer} event with `from` set to the zero address.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     */
    function _mint(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: mint to the zero address");

        _beforeTokenTransfer(address(0), account, amount);

        _totalSupply = _totalSupply.add(amount);
        _balances[account] = _balances[account].add(amount);
        emit Transfer(address(0), account, amount);
    }

    /**
     * @dev Destroys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a {Transfer} event with `to` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    function _burn(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: burn from the zero address");

        _beforeTokenTransfer(account, address(0), amount);

        _balances[account] = _balances[account].sub(amount, "ERC20: burn amount exceeds balance");
        _totalSupply = _totalSupply.sub(amount);
        emit Transfer(account, address(0), amount);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
     *
     * This internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(address owner, address spender, uint256 amount) internal virtual {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    /**
     * @dev Sets {decimals} to a value other than the default one of 18.
     *
     * WARNING: This function should only be called from the constructor. Most
     * applications that interact with token contracts will not expect
     * {decimals} to ever change, and may work incorrectly if it does.
     */
    function _setupDecimals(uint8 decimals_) internal virtual {
        _decimals = decimals_;
    }

    /**
     * @dev Hook that is called before any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * will be to transferred to `to`.
     * - when `from` is zero, `amount` tokens will be minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(address from, address to, uint256 amount) internal virtual { }
}

// File: contracts\Cvx.sol

pragma solidity 0.6.12;


contract ConvexToken is ERC20{
    using SafeERC20 for IERC20;
    using Address for address;
    using SafeMath for uint256;

    address public operator;
    address public vecrvProxy;

    uint256 public maxSupply = 100 * 1000000 * 1e18; //100mil
    uint256 public totalCliffs = 1000;
    uint256 public reductionPerCliff;

    constructor(address _proxy)
        public
        ERC20(
            "Convex Token",
            "CVX"
        )
    {
        operator = msg.sender;
        vecrvProxy = _proxy;
        reductionPerCliff = maxSupply.div(totalCliffs);
    }

    //get current operator off proxy incase there was a change
    function updateOperator() public {
        operator = IStaker(vecrvProxy).operator();
    }
    
    function mint(address _to, uint256 _amount) external {
        if(msg.sender != operator){
            //dont error just return. if a shutdown happens, rewards on old system
            //can still be claimed, just wont mint cvx
            return;
        }

        uint256 supply = totalSupply();
        if(supply == 0){
            //premine, one time only
            _mint(_to,_amount);
            //automatically switch operators
            updateOperator();
            return;
        }
        
        //use current supply to gauge cliff
        //this will cause a bit of overflow into the next cliff range
        //but should be within reasonable levels.
        //requires a max supply check though
        uint256 cliff = supply.div(reductionPerCliff);
        //mint if below total cliffs
        if(cliff < totalCliffs){
            //for reduction% take inverse of current cliff
            uint256 reduction = totalCliffs.sub(cliff);
            //reduce
            _amount = _amount.mul(reduction).div(totalCliffs);

            //supply cap check
            uint256 amtTillMax = maxSupply.sub(supply);
            if(_amount > amtTillMax){
                _amount = amtTillMax;
            }

            //mint
            _mint(_to, _amount);
        }
    }

}