// File: /Users/Alle588/Desktop/WORK/PROVABLE/steroids.finance-contracts/contracts/IRewardDistributionRecipient.sol



pragma solidity ^0.5.0;

import "@openzeppelin/contracts/ownership/Ownable.sol";


contract IRewardDistributionRecipient is Ownable {
    address public rewardDistribution;

    function notifyRewardAmount(uint256 reward) external;

    modifier onlyRewardDistribution() {
        require(_msgSender() == rewardDistribution, "Caller is not reward distribution");
        _;
    }

    function setRewardDistribution(address _rewardDistribution) external onlyOwner {
        rewardDistribution = _rewardDistribution;
    }
}

// File: /Users/Alle588/Desktop/WORK/PROVABLE/steroids.finance-contracts/contracts/ModifiedUnipool.sol



pragma solidity ^0.5.0;

import "@openzeppelin/contracts/math/Math.sol";
import "@openzeppelin/contracts/math/SafeMath.sol";
import "@openzeppelin/contracts/ownership/Ownable.sol";
import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
import "./IRewardDistributionRecipient.sol";


contract LPTokenWrapper {
    using SafeMath for uint256;
    using SafeERC20 for IERC20;

    IERC20 public uniV2;

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

    event Approval(address indexed owner, address indexed spender, uint256 value);

    constructor(address _uniV2) public {
        uniV2 = IERC20(_uniV2);
    }

    function totalSupply() public view returns (uint256) {
        return _totalSupply;
    }

    function balanceOf(address account) public view returns (uint256) {
        return _balances[account];
    }

    function stakeFor(address _user, uint256 _amount) public {
        _stake(_user, _amount);
    }

    function stake(uint256 _amount) public {
        _stake(msg.sender, _amount);
    }

    function approve(address _user, uint256 _amount) public {
        _approve(msg.sender, _user, _amount);
    }

    function withdraw(uint256 _amount) public {
        _withdraw(msg.sender, _amount);
    }

    function withdrawFrom(address _user, uint256 _amount) public {
        _withdraw(_user, _amount);
        _approve(
            _user,
            msg.sender,
            _allowances[_user][msg.sender].sub(
                _amount,
                "LPTokenWrapper: transfer amount exceeds allowance"
            )
        );
    }

    function allowance(address _owner, address _spender) public view returns (uint256) {
        return _allowances[_owner][_spender];
    }

    function _stake(address _user, uint256 _amount) internal {
        _totalSupply = _totalSupply.add(_amount);
        _balances[_user] = _balances[_user].add(_amount);
        uniV2.safeTransferFrom(msg.sender, address(this), _amount);
    }

    function _withdraw(address _owner, uint256 _amount) internal {
        _totalSupply = _totalSupply.sub(_amount);
        _balances[_owner] = _balances[_owner].sub(_amount);
        IERC20(uniV2).safeTransfer(msg.sender, _amount);
    }

    function _approve(
        address _owner,
        address _user,
        uint256 _amount
    ) internal returns (bool) {
        require(_user != address(0), "LPTokenWrapper: approve to the zero address");
        _allowances[_owner][_user] = _amount;
        emit Approval(_owner, _user, _amount);
        return true;
    }
}


contract ModifiedUnipool is LPTokenWrapper, IRewardDistributionRecipient {
    address public rewardToken;
    uint256 public constant DURATION = 7 days;

    uint256 public periodFinish = 0;
    uint256 public rewardRate = 0;
    uint256 public lastUpdateTime;
    uint256 public rewardPerTokenStored;
    mapping(address => uint256) public userRewardPerTokenPaid;
    mapping(address => uint256) public rewards;

    event RewardAdded(uint256 reward);
    event Staked(address indexed user, uint256 amount);
    event Withdrawn(address indexed user, uint256 amount);
    event RewardPaid(address indexed user, uint256 reward);

    modifier updateReward(address account) {
        rewardPerTokenStored = rewardPerToken();
        lastUpdateTime = lastTimeRewardApplicable();
        if (account != address(0)) {
            rewards[account] = earned(account);
            userRewardPerTokenPaid[account] = rewardPerTokenStored;
        }
        _;
    }

    constructor(address _rewardToken, address _uniV2) public LPTokenWrapper(_uniV2) {
        rewardToken = _rewardToken;
    }

    function notifyRewardAmount(uint256 reward)
        external
        onlyRewardDistribution
        updateReward(address(0))
    {
        if (block.timestamp >= periodFinish) {
            rewardRate = reward.div(DURATION);
        } else {
            uint256 remaining = periodFinish.sub(block.timestamp);
            uint256 leftover = remaining.mul(rewardRate);
            rewardRate = reward.add(leftover).div(DURATION);
        }
        lastUpdateTime = block.timestamp;
        periodFinish = block.timestamp.add(DURATION);
        emit RewardAdded(reward);
    }

    function exit() external {
        withdraw(balanceOf(msg.sender));
        getReward(msg.sender);
    }

    function lastTimeRewardApplicable() public view returns (uint256) {
        return Math.min(block.timestamp, periodFinish);
    }

    function rewardPerToken() public view returns (uint256) {
        if (totalSupply() == 0) {
            return rewardPerTokenStored;
        }
        return
            rewardPerTokenStored.add(
                lastTimeRewardApplicable().sub(lastUpdateTime).mul(rewardRate).mul(1e18).div(
                    totalSupply()
                )
            );
    }

    function earned(address account) public view returns (uint256) {
        return
            balanceOf(account)
                .mul(rewardPerToken().sub(userRewardPerTokenPaid[account]))
                .div(1e18)
                .add(rewards[account]);
    }

    function stake(uint256 amount) public updateReward(msg.sender) {
        require(amount > 0, "Cannot stake 0");
        super.stake(amount);
        emit Staked(msg.sender, amount);
    }

    function stakeFor(address _user, uint256 _amount) public updateReward(_user) {
        require(_amount > 0, "Cannot stake 0");
        super.stakeFor(_user, _amount);
        emit Staked(_user, _amount);
    }

    function withdraw(uint256 amount) public updateReward(msg.sender) {
        require(amount > 0, "Cannot withdraw 0");
        super.withdraw(amount);
        emit Withdrawn(msg.sender, amount);
    }

    function withdrawFrom(address _user, uint256 amount) public updateReward(_user) {
        require(amount > 0, "Cannot withdraw 0");
        super.withdrawFrom(_user, amount);
        emit Withdrawn(_user, amount);
    }

    function getReward() public {
        _getReward(msg.sender);
    }

    function getReward(address _user) public {
        _getReward(_user);
    }

    function _getReward(address _user) internal updateReward(_user) {
        uint256 reward = earned(_user);
        if (reward > 0) {
            rewards[_user] = 0;
            IERC20(rewardToken).safeTransfer(_user, reward);
            emit RewardPaid(_user, reward);
        }
    }
}

// File: /Users/Alle588/Desktop/WORK/PROVABLE/steroids.finance-contracts/contracts/interfaces/IWETH.sol



pragma solidity >=0.5.0;

interface IWETH {
    function deposit() external payable;

    function transfer(address to, uint256 value) external returns (bool);

    function withdraw(uint256) external;

    function balanceOf(address who) external view returns (uint256);

    function approve(address spender, uint256 amount) external returns (bool);

    function allowance(address owner, address spender) external returns (uint256);
}

// File: /Users/Alle588/Desktop/WORK/PROVABLE/steroids.finance-contracts/contracts/lib/UniswapV2Library.sol



// taken from here: https://github.com/Uniswap/uniswap-v2-periphery/blob/master/contracts/libraries/UniswapV2Library.sol
pragma solidity >=0.5.0;

import "@openzeppelin/contracts/math/SafeMath.sol";


library UniswapV2Library {
    using SafeMath for uint256;

    // given an input amount of an asset and pair reserves, returns the maximum output amount of the other asset
    function getAmountOut(
        uint256 amountIn,
        uint256 reserveIn,
        uint256 reserveOut
    ) internal pure returns (uint256 amountOut) {
        require(amountIn > 0, "UniswapV2Library: INSUFFICIENT_INPUT_AMOUNT");
        require(reserveIn > 0 && reserveOut > 0, "UniswapV2Library: INSUFFICIENT_LIQUIDITY");
        uint256 amountInWithFee = amountIn.mul(997);
        uint256 numerator = amountInWithFee.mul(reserveOut);
        uint256 denominator = reserveIn.mul(1000).add(amountInWithFee);
        amountOut = numerator / denominator;
    }

    /**
     * @author allemanfredi
     * @notice given an input amount, returns the output
     *         amount with slippage and with fees. This fx is
     *         to check approximately onchain the slippage
     *         during a swap
     */
    function calculateSlippageAmountWithFees(
        uint256 _amountIn,
        uint256 _allowedSlippage,
        uint256 _rateIn,
        uint256 _rateOut
    ) internal pure returns (uint256) {
        require(_amountIn > 0, "UniswapV2Library: INSUFFICIENT_INPUT_AMOUNT");
        uint256 slippageAmount = _amountIn
            .mul(_rateOut)
            .div(_rateIn)
            .mul(10000 - _allowedSlippage)
            .div(10000);
        // NOTE: remove fees
        return slippageAmount.mul(997).div(1000);
    }

    /**
     * @author allemanfredi
     * @notice given 2 inputs amount, it returns the
     *         rate percentage between the 2 amounts
     */
    function calculateRate(uint256 _amountIn, uint256 _amountOut) internal pure returns (uint256) {
        require(_amountIn > 0, "UniswapV2Library: INSUFFICIENT_INPUT_AMOUNT");
        require(_amountOut > 0, "UniswapV2Library: INSUFFICIENT_OUTPUT_AMOUNT");
        return
            _amountIn > _amountOut
                ? (10000 * _amountIn).sub(10000 * _amountOut).div(_amountIn)
                : (10000 * _amountOut).sub(10000 * _amountIn).div(_amountOut);
    }

    /**
     * @author allemanfredi
     * @notice returns the slippage for a trade without counting the fees
     */
    function calculateSlippage(
        uint256 _amountIn,
        uint256 _reserveIn,
        uint256 _reserveOut
    ) internal pure returns (uint256) {
        require(_amountIn > 0, "UniswapV2Library: INSUFFICIENT_INPUT_AMOUNT");
        uint256 price = _reserveOut.mul(10**18).div(_reserveIn);
        uint256 quote = _amountIn.mul(price);
        uint256 amountOut = getAmountOut(_amountIn, _reserveIn, _reserveOut);
        return uint256(10000).sub((amountOut * 10000).div(quote.div(10**18))).mul(997).div(1000);
    }
}

// File: /Users/Alle588/Desktop/WORK/PROVABLE/steroids.finance-contracts/contracts/strategies/RewardedPltcWethUniV2Pair.sol



pragma solidity ^0.5.0;

import "@openzeppelin/contracts/math/SafeMath.sol";
import "@openzeppelin/contracts/utils/Address.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
import "@openzeppelin/contracts/ownership/Ownable.sol";
import "@uniswap/v2-core/contracts/interfaces/IUniswapV2Pair.sol";
import "../lib/UniswapV2Library.sol";
import "../ModifiedUnipool.sol";
import "../interfaces/IWETH.sol";


contract RewardedPltcWethUniV2Pair is Ownable {
    using SafeMath for uint256;
    using SafeERC20 for IERC20;

    IERC20 public pltc;
    IWETH public weth;
    IUniswapV2Pair public uniV2;
    ModifiedUnipool public modifiedUnipool;

    uint256 public allowedSlippage;

    event Staked(address indexed user, uint256 amount);
    event Unstaked(address indexed user, uint256 pltcAmount, uint256 ethAmount);
    event AllowedSlippageChanged(uint256 slippage);

    /**
     * @param _uniV2 UniV2Pair address
     * @param _modifiedUnipool ModifiedUnipool address
     */
    constructor(address _uniV2, address _modifiedUnipool) public {
        require(Address.isContract(_uniV2), "RewardedPltcWethUniV2Pair: _uniV2 not a contract");

        uniV2 = IUniswapV2Pair(_uniV2);
        modifiedUnipool = ModifiedUnipool(_modifiedUnipool);
        pltc = IERC20(uniV2.token0());
        weth = IWETH(uniV2.token1());
    }

    /**
     * @notice function used to handle the ethers sent
     *         during the witdraw within the unstake function
     */
    function() external payable {
        require(msg.sender == address(weth), "RewardedPltcWethUniV2Pair: msg.sender is not weth");
    }

    /**
     *  @param _allowedSlippage new max allowed in percentage
     */
    function setAllowedSlippage(uint256 _allowedSlippage) external onlyOwner {
        allowedSlippage = _allowedSlippage;
        emit AllowedSlippageChanged(_allowedSlippage);
    }

    /**
     * @notice _stakeFor wrapper
     */
    function stake() public payable returns (bool) {
        require(msg.value > 0, "RewardedPltcWethUniV2Pair: msg.value must be greater than 0");
        _stakeFor(msg.sender, msg.value);
        return true;
    }

    /**
     * @notice Burn all user's UniV2 staked in the ModifiedUnipool,
     *         unwrap the corresponding amount of WETH into ETH, collect
     *         rewards matured from the UniV2 staking and sent it to msg.sender.
     *         User must approve this contract to withdraw the corresponding
     *         amount of his UniV2 balance in behalf of him.
     */
    function unstake() public returns (bool) {
        uint256 uniV2SenderBalance = modifiedUnipool.balanceOf(msg.sender);
        require(
            modifiedUnipool.allowance(msg.sender, address(this)) >= uniV2SenderBalance,
            "RewardedPltcWethUniV2Pair: amount not approved"
        );

        modifiedUnipool.withdrawFrom(msg.sender, uniV2SenderBalance);
        modifiedUnipool.getReward(msg.sender);

        uniV2.transfer(address(uniV2), uniV2SenderBalance);
        (uint256 pltcAmount, uint256 wethAmount) = uniV2.burn(address(this));

        weth.withdraw(wethAmount);
        address(msg.sender).transfer(wethAmount);
        pltc.transfer(msg.sender, pltcAmount);

        emit Unstaked(msg.sender, pltcAmount, wethAmount);
        return true;
    }

    /**
     * @notice Wrap the Ethereum sent into WETH, swap the amount sent / 2
     *         into WETH and put them into a PLTC/WETH Uniswap pool.
     *         The amount of UniV2 token will be sent to ModifiedUnipool
     *         in order to mature rewards.
     * @param _user address of the user who will have UniV2 tokens in ModifiedUnipool
     * @param _amount amount of weth to use to perform this operation
     */
    function _stakeFor(address _user, uint256 _amount) internal {
        uint256 wethAmountIn = _amount / 2;
        (uint256 pltcReserve, uint256 wethReserve, ) = uniV2.getReserves();
        uint256 pltcAmountOut = UniswapV2Library.getAmountOut(wethAmountIn, wethReserve, pltcReserve);

        require(
            allowedSlippage >=
                UniswapV2Library.calculateSlippage(wethAmountIn, wethReserve, pltcReserve),
            "RewardedPltcWethUniV2Pair: too much slippage"
        );

        weth.deposit.value(_amount)();
        weth.transfer(address(uniV2), wethAmountIn);
        uniV2.swap(pltcAmountOut, 0, address(this), "");

        pltc.safeTransfer(address(uniV2), pltcAmountOut);
        weth.transfer(address(uniV2), wethAmountIn);
        uint256 liquidity = uniV2.mint(address(this));

        uniV2.approve(address(modifiedUnipool), liquidity);
        modifiedUnipool.stakeFor(_user, liquidity);

        emit Staked(_user, _amount);
    }
}

// File: @openzeppelin/contracts/GSN/Context.sol



pragma solidity ^0.5.0;

/*
 * @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.
 */
contract Context {
    // Empty internal constructor, to prevent people from mistakenly deploying
    // an instance of this contract, which should be used via inheritance.
    constructor () internal { }
    // solhint-disable-previous-line no-empty-blocks

    function _msgSender() internal view returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view 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/math/Math.sol



pragma solidity ^0.5.0;

/**
 * @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/math/SafeMath.sol



pragma solidity ^0.5.0;

/**
 * @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, 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) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     *
     * _Available since v2.4.0._
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    /**
     * @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) {
        // 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 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts 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) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message 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.
     *
     * _Available since v2.4.0._
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts 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) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message 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.
     *
     * _Available since v2.4.0._
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

// File: @openzeppelin/contracts/ownership/Ownable.sol



pragma solidity ^0.5.0;

import "../GSN/Context.sol";
/**
 * @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.
 *
 * 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.
 */
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 {
        _owner = _msgSender();
        emit OwnershipTransferred(address(0), _owner);
    }

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

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

    /**
     * @dev Returns true if the caller is the current owner.
     */
    function isOwner() public view returns (bool) {
        return _msgSender() == _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 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 onlyOwner {
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     */
    function _transferOwnership(address newOwner) internal {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

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



pragma solidity ^0.5.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP. Does not include
 * the optional functions; to access them see {ERC20Detailed}.
 */
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/token/ERC20/SafeERC20.sol



pragma solidity ^0.5.0;

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 ERC20;` 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));
    }

    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.

        // A Solidity high level call has three parts:
        //  1. The target address is checked to verify it contains contract code
        //  2. The call itself is made, and success asserted
        //  3. The return value is decoded, which in turn checks the size of the returned data.
        // solhint-disable-next-line max-line-length
        require(address(token).isContract(), "SafeERC20: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = address(token).call(data);
        require(success, "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/utils/Address.sol



pragma solidity ^0.5.5;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * This test is non-exhaustive, and there may be false-negatives: during the
     * execution of a contract's constructor, its address will be reported as
     * not containing 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.
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies in extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        // According to EIP-1052, 0x0 is the value returned for not-yet created accounts
        // and 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470 is returned
        // for accounts without code, i.e. `keccak256('')`
        bytes32 codehash;
        bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;
        // solhint-disable-next-line no-inline-assembly
        assembly { codehash := extcodehash(account) }
        return (codehash != 0x0 && codehash != accountHash);
    }

    /**
     * @dev Converts an `address` into `address payable`. Note that this is
     * simply a type cast: the actual underlying value is not changed.
     *
     * _Available since v2.4.0._
     */
    function toPayable(address account) internal pure returns (address payable) {
        return address(uint160(account));
    }

    /**
     * @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].
     *
     * _Available since v2.4.0._
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

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

// File: @uniswap/v2-core/contracts/interfaces/IUniswapV2Pair.sol



pragma solidity >=0.5.0;

interface IUniswapV2Pair {
    event Approval(address indexed owner, address indexed spender, uint value);
    event Transfer(address indexed from, address indexed to, uint value);

    function name() external pure returns (string memory);
    function symbol() external pure returns (string memory);
    function decimals() external pure returns (uint8);
    function totalSupply() external view returns (uint);
    function balanceOf(address owner) external view returns (uint);
    function allowance(address owner, address spender) external view returns (uint);

    function approve(address spender, uint value) external returns (bool);
    function transfer(address to, uint value) external returns (bool);
    function transferFrom(address from, address to, uint value) external returns (bool);

    function DOMAIN_SEPARATOR() external view returns (bytes32);
    function PERMIT_TYPEHASH() external pure returns (bytes32);
    function nonces(address owner) external view returns (uint);

    function permit(address owner, address spender, uint value, uint deadline, uint8 v, bytes32 r, bytes32 s) external;

    event Mint(address indexed sender, uint amount0, uint amount1);
    event Burn(address indexed sender, uint amount0, uint amount1, address indexed to);
    event Swap(
        address indexed sender,
        uint amount0In,
        uint amount1In,
        uint amount0Out,
        uint amount1Out,
        address indexed to
    );
    event Sync(uint112 reserve0, uint112 reserve1);

    function MINIMUM_LIQUIDITY() external pure returns (uint);
    function factory() external view returns (address);
    function token0() external view returns (address);
    function token1() external view returns (address);
    function getReserves() external view returns (uint112 reserve0, uint112 reserve1, uint32 blockTimestampLast);
    function price0CumulativeLast() external view returns (uint);
    function price1CumulativeLast() external view returns (uint);
    function kLast() external view returns (uint);

    function mint(address to) external returns (uint liquidity);
    function burn(address to) external returns (uint amount0, uint amount1);
    function swap(uint amount0Out, uint amount1Out, address to, bytes calldata data) external;
    function skim(address to) external;
    function sync() external;

    function initialize(address, address) external;
}