function approve(address spender, uint256 value) public returns (bool);
  event Approval(
    address indexed owner,
    address indexed spender,
    uint256 value
  );
}




pragma solidity 0.4.24;



contract FlashLender is ReentrancyGuard, Ownable {
    using SafeMath for uint256;

    string public version = '0.1';
    address public bank;
    uint256 public fee;
    
    
    modifier isArbitrage(address token, uint256 amount) {
        uint256 balance = IBank(bank).totalSupplyOf(token);
        uint256 feeAmount = amount.mul(fee).div(10 ** 18); 
        _;
        require(IBank(bank).totalSupplyOf(token) >= (balance.add(feeAmount)));
    }