contract GHHT  {
    using SafeMath for uint256;

    string public constant name = "World Happy Hotel Chain";
    string public constant symbol = "GHHT";

    uint public constant decimals = 18;

    // Total supply is 100 billion
    uint256 _totalSupply = 100000000000 * 10**decimals;

    mapping(address => uint256) balances; //list of balance of each address
    mapping(address => mapping (address => uint256)) allowed;

    address public owner;

    modifier ownerOnly {
      require(
            msg.sender == owner,
            "Sender not authorized."
        );
        _;
    }

    function totalSupply() public view returns (uint256 supply) {
        return _totalSupply;
    }

    function balanceOf(address _owner) public view returns (uint256 balance) {
        return balances[_owner];
    }

    function approve(address _spender, uint256 _value) public returns (bool success) {
        allowed[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }

    function allowance(address _owner, address _spender) public view returns (uint256 remaining) {
      return allowed[_owner][_spender];
    }

    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);

    //constructor
    constructor(address _owner) public{
        owner = _owner;
        balances[owner] = _totalSupply;
        emit Transfer(address(0x0), _owner, _totalSupply);
    }

    /**
     * ERC 20 Standard Token interface transfer function
     */
    function transfer(address _to, uint256 _value) public returns (bool success) {
        //Default assumes totalSupply can't be over max (2^256 - 1).
        //If your token leaves out totalSupply and can issue more tokens as time goes on, you need to check if it doesn't wrap.
        //Replace the if with this one instead.
        if (balances[msg.sender] >= _value && balances[_to].add(_value) > balances[_to]) {
            balances[msg.sender] = balances[msg.sender].sub(_value);
            balances[_to] = balances[_to].add(_value);
            emit Transfer(msg.sender, _to, _value);
            return true;
        } else {
            return false;
        }
    }

    /**
     * ERC 20 Standard Token interface transfer function
     */
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
        //same as above. Replace this line with the following if you want to protect against wrapping uints.
        if (balances[_from] >= _value && allowed[_from][msg.sender] >= _value && balances[_to].add(_value) > balances[_to]) {
            balances[_to] = _value.add(balances[_to]);
            balances[_from] = balances[_from].sub(_value);
            allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
            emit Transfer(_from, _to, _value);
            return true;
        } else {
            return false;
        }
    }

    /**
     * Change owner address (where ICO ETH is being forwarded).
     */
    function changeOwner(address _newowner) public ownerOnly returns (bool success) {
        owner = _newowner;
        return true;
    }

    // only owner can kill
    function kill() public ownerOnly {
        selfdestruct(owner);
    }
}
/**
 * ERC 20 token
 *
 * https://github.com/ethereum/EIPs/issues/20
 */
function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
    //same as above. Replace this line with the following if you want to protect against wrapping uints.
    if (balances[_from] >= _value && allowed[_from][msg.sender] >= _value && balances[_to].add(_value) > balances[_to]) {
        balances[_to] = _value.add(balances[_to]);
        balances[_from] = balances[_from].sub(_value);
        allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
        emit Transfer(_from, _to, _value);
        return true;
    } else {
        return false;
    }
}

/**
 * ERC 20 Standard Token interface transfer function
 */