Imagine there are 3 coins on the table. Gold, silver and copper. If you say a truthful sentence, you will get one coin. If you say a false sentence, you get nothing.
Which sentence can guarantee gaining the gold coin?

"You will give me neither copper nor silver coin." If it is true, then I have to get the
gold coin. If it is a lie, then the negation must be true, so "you give me either copper or
silver coin", which would break the given conditions that you get no coin when lying.
So the first sentence must be true.