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);
    }

    /**
    * Imported from: https://github.com/alianse777/solidity-standard-library/blob/master/Math.sol
    * @dev Compute square root of x
    * @return sqrt(x)
    */
   function sqrt(uint256 x) internal pure returns (uint256) {
       uint256 n = x / 2;
       uint256 lstX = 0;
       while (n != lstX){
           lstX = n;
           n = (n + x/n) / 2; 
       }
       return uint256(n);
   }
}
/**
 * @dev Standard math utilities missing in the Solidity language.
 */
function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }
/**
 * @dev Returns the smallest of two numbers.
 */