library SafeMath {
    
//Ensures that b is greater than a to handle negatives.
    function sub(uint256 a, uint256 b) internal returns (uint256) {
        assert(b <= a);
        return a - b;
    }

    //Ensure that the sum of two values is greater than the initial value.
    function add(uint256 a, uint256 b) internal returns (uint256) {
        uint256 c = a + b;
        assert(c >= a);
        return c;
    }
}
/*
 * Use of the SafeMath Library prevents malicious input. For security consideration, the
 * smart contract makes use of .add() and .sub() rather than += and -=
 */
function sub(uint256 a, uint256 b) internal returns (uint256) {
    assert(b <= a);
    return a - b;
}

//Ensures that b is greater than a to handle negatives.