library SafeMath {
    function add(uint a, uint b) internal pure returns (uint c) {
        c = a + b;
        require(c >= a);
    }
    function sub(uint a, uint b) internal pure returns (uint c) {
        require(b <= a);
        c = a - b;
    }
    function mul(uint a, uint b) internal pure returns (uint c) {
        c = a * b;
        require(a == 0 || c / a == b);
    }
    function div(uint a, uint b) internal pure returns (uint c) {
        require(b > 0);
        c = a / b;
    }
    
     //not a SafeMath function
    function max(uint a, uint b) private pure returns (uint) {
        return a > b ? a : b;
    }
    
}
// Safe math
function max(uint a, uint b) private pure returns (uint) {
    return a > b ? a : b;
}

//not a SafeMath function