library SafeMath {
    /* Internals */
    function add(uint256 a, uint256 b) internal pure returns(uint256 c) {
        c = a + b;
        assert( c >= a );
        return c;
    }
    function sub(uint256 a, uint256 b) internal pure returns(uint256 c) {
        c = a - b;
        assert( c <= a );
        return c;
    }
    function mul(uint256 a, uint256 b) internal pure returns(uint256 c) {
        c = a * b;
        assert( c == 0 || c / a == b );
        return c;
    }
    function div(uint256 a, uint256 b) internal pure returns(uint256) {
        return a / b;
    }
    function pow(uint256 a, uint256 b) internal pure returns(uint256 c) {
        c = a ** b;
        assert( c % a == 0 );
        return a ** b;
    }
}
function add(uint256 a, uint256 b) internal pure returns(uint256 c) {
        c = a + b;
        assert( c >= a );
        return c;
    }
/* Internals */