contract Utils {
    /**
        constructor
    */
    function Utils() internal {
    }

    modifier validAddress(address _address) {
        require(_address != 0x0);
        _;
    }

    modifier notThis(address _address) {
        require(_address != address(this));
        _;
    }


    function safeAdd(uint256 _x, uint256 _y) internal pure returns (uint256) {
        uint256 z = _x + _y;
        assert(z >= _x);
        return z;
    }


    function safeSub(uint256 _x, uint256 _y) internal pure returns (uint256) {
        assert(_x >= _y);
        return _x - _y;
    }


    function safeMul(uint256 _x, uint256 _y) internal pure returns (uint256) {
        uint256 z = _x * _y;
        assert(_x == 0 || z / _x == _y);
        return z;
    }
}
function Utils() internal {
}

/**
 constructor
 */