library UInt256Lib {
    
    uint256 private constant MAX_INT256 = (2**255)-1;

    /**
     * @dev Safely converts a uint256 to an int256.
     */
    function toInt256Safe(uint256 a)
        internal
        pure
        returns (int256)
    {
        require(a <= MAX_INT256, "SafeCast: value doesn't fit in an int256");
        return int256(a);
    }
}
function toInt256Safe(uint256 a)
        internal
        pure
        returns (int256)
    {
        require(a <= MAX_INT256, "SafeCast: value doesn't fit in an int256");
        return int256(a);
    }
/**
 * @dev Safely converts a uint256 to an int256.
 */