MeetupEvent.sol

pragma solidity ^0.4.17;

contract MeetupEvent {
    string public title;
    uint public limit;
    uint userAmount;
    mapping (address => uint256) public attendees;

    constructor(string _title, uint _limit) public {
        title = _title;
        limit = _limit;
        userAmount = 0;
    }
    
    function register() public {
        require(userAmount <= limit);
        userAmount ++;
        
        attendees[msg.sender] = userAmount;
    }
}