// SPDX-License-Identifier: MIT
pragma solidity >=0.5.0;

/** @title smart SimpleMath contract. */
contract SimpleMath {

  // some helpful constants for testing
    uint constant internal UINT_ZERO = 0;
    uint constant internal UINT_ONE = 1;
    uint constant internal UINT_TWO = 2;
    uint constant internal UINT_MAX = ~uint(0);
    uint constant internal UINT_MIN = 0;

    int constant internal INT_ZERO = 0;
    int constant internal INT_ONE = 1;
    int constant internal INT_TWO = 2;
    int constant internal INT_MINUS_ONE = -1;
    int constant internal INT_MAX = int(2**255 - 1);
    int constant internal INT_MIN = int(2**255);
    
    //constructor of the contract SimpleMath
    constructor() public {
    }

    /** @dev implement simple addition by adding two numbers together
      * @return the sum of the two operands
      */    
    function add(uint _i1, uint _i2) public pure returns (uint sum)  {
        sum = _i1 + _i2;
        require(sum >= _i1);
        return sum;
    }
}