## 170.

Once I asked a passerby: "Are you a vampire who has lost your mind?" He answered either "yes" or "no," and I found out what type he was.

Who was he?
170. A sane person would answer my question negatively, while Transylvanians of any of the other three types would answer affirmatively. Receiving an affirmative answer to my question, I would not be able to determine which of the four types of Transylvanians my interlocutor belongs to. But according to the conditions of the problem, I learned from the answer who my interlocutor was. Therefore, he did not answer affirmatively. This means he answered "no," from which we conclude that the Transylvanian was a sane person.