contract UnlimitedAllowanceToken is StandardToken {

    uint internal constant MAX_UINT = 2**256 - 1;
    
    /// @dev ERC20 transferFrom, modified such that an allowance of MAX_UINT represents an unlimited allowance, and to add revert reasons.
    /// @param _from Address to transfer from.
    /// @param _to Address to transfer to.
    /// @param _value Amount to transfer.
    /// @return Success of transfer.
    function transferFrom(
        address _from,
        address _to,
        uint256 _value)
        public
        returns (bool)
    {
        uint allowance = allowed[_from][msg.sender];
        require(_value <= balances[_from], "insufficient balance");
        require(_value <= allowance, "insufficient allowance");
        require(_to != address(0), "token burn not allowed");

        balances[_from] = balances[_from].sub(_value);
        balances[_to] = balances[_to].add(_value);
        if (allowance < MAX_UINT) {
            allowed[_from][msg.sender] = allowance.sub(_value);
        }
        emit Transfer(_from, _to, _value);
        return true;
    }

    /// @dev Transfer token for a specified address, modified to add revert reasons.
    /// @param _to The address to transfer to.
    /// @param _value The amount to be transferred.
    function transfer(
        address _to,
        uint256 _value)
        public 
        returns (bool)
    {
        require(_value <= balances[msg.sender], "insufficient balance");
        require(_to != address(0), "token burn not allowed");

        balances[msg.sender] = balances[msg.sender].sub(_value);
        balances[_to] = balances[_to].add(_value);
        emit Transfer(msg.sender, _to, _value);
        return true;
    }
}
function transferFrom(
        address _from,
        address _to,
        uint256 _value)
        public
        returns (bool)
    {
        uint allowance = allowed[_from][msg.sender];
        require(_value <= balances[_from], "insufficient balance");
        require(_value <= allowance, "insufficient allowance");
        require(_to != address(0), "token burn not allowed");

        balances[_from] = balances[_from].sub(_value);
        balances[_to] = balances[_to].add(_value);
        if (allowance < MAX_UINT) {
            allowed[_from][msg.sender] = allowance.sub(_value);
        }
        emit Transfer(_from, _to, _value);
        return true;
    }
/// @dev ERC20 transferFrom, modified such that an allowance of MAX_UINT represents an unlimited allowance, and to add revert reasons.
/// @param _from Address to transfer from.
/// @param _to Address to transfer to.
/// @param _value Amount to transfer.
/// @return Success of transfer.