Hello World Solidity Smart Contract

HelloWorld.sol.js

pragma solidity ^0.5.2;

contract HelloWorld {
    
    uint public num;
    
    event NewNum(address indexed _who, uint _newNum, uint _timestamp);
    
    constructor(uint _num) public {
        num = _num;
    }
    
    function setNum(uint _newNum) public {
        num = _newNum;
        emit NewNum(msg.sender, _newNum, now);
    }
}