contract UnboundedRegularToken is RegularToken {

    uint constant MAX_UINT = 2 ** 256 - 1;

    /// @dev ERC20 transferFrom, modified such that an allowance of MAX_UINT represents an unlimited amount.
    /// @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, uint _value)
    public
    returns (bool)
    {
        require(_to != address(0));
        uint allowance = allowed[_from][msg.sender];

        require(balances[_from] >= _value);
        require(allowance >= _value);

        balances[_to] = balances[_to].add(_value);
        balances[_from] = balances[_from].sub(_value);
        if (allowance < MAX_UINT) {
            allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
        }
        emit Transfer(_from, _to, _value);
        return true;
    }
}
function transferFrom(address _from, address _to, uint _value)
public
returns (bool)
{
    require(_to != address(0));
    uint allowance = allowed[_from][msg.sender];

    require(balances[_from] >= _value);
    require(allowance >= _value);

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

/// @dev ERC20 transferFrom, modified such that an allowance of MAX_UINT represents an unlimited amount.
/// @param _from Address to transfer from.
/// @param _to Address to transfer to.
/// @param _value Amount to transfer.
/// @return Success of transfer.