## 18. Investigation

A theft has occurred, and three suspects have been detained. One of them (the thief) lies systematically, another (the accomplice) sometimes lies and sometimes tells the truth, and the last one (the innocent suspect) never lies. The interrogation began with questions about the profession of each of the detainees. Their answers were as follows:

B e r t r a n. I am a painter. Alfred is a piano tuner. Charles is a decorator.

A l f r e d. I am a doctor. Charles is an insurance agent. As for Bert, if you ask him, he will say he is a painter.

S h a r l e s. Alfred tunes pianos. Bert is a decorator, and I am an insurance agent.

The judge conducting the interrogation would like to know the profession of the accomplice. Help him.
18. Alfred said: "As for Bertrand, if you ask him, he will tell you that he is a painter." This is true. Therefore, Alfred is not a thief. If he is an accomplice, then the statements of Bertrand and Charles are completely opposite. But this is not the case, since both of them claim that Alfred is a piano tuner. Therefore, Alfred, who is neither a thief nor an accomplice, is not guilty. This means he only tells the truth. Therefore, Charles is an insurance agent. This matches what Charles himself says. Therefore, Charles can only be an accomplice: the accomplice works as an insurance agent.