SimpleContract.sol

pragma solidity ^0.4.24;

contract SimpleContract {
    uint public paymentCount = 0;
    
    event PaymentReceived(uint value, address sender);
    
    address public owner;
    
    constructor() public {
        owner = msg.sender;
    }
    
    function () public payable {
        paymentCount += 1;
        emit PaymentReceived(msg.value, msg.sender);
    }
    
    function balance() public view returns(uint) {
        return address(this).balance;
    }
    
    modifier isOwner() {
        require(msg.sender == owner, "Must be the owner");
        _;
    }
    
    function withdraw() public isOwner {
        owner.transfer(this.balance());

    }
}