5.4. At the crossroads, four travelers met: inhabitants of the city of liars (who always lie) and the city of knights (who always tell the truth) (not all were from the same city). The first said: “Besides me, there is exactly one inhabitant of my city here.” The second added: “And I am the only one from my city.” The third confirmed the second's words: “You are right.” The fourth remained silent. From which city is the fourth?
Solution. From the third statement, it follows that he is from the same city as the second, but then the second cannot be telling the truth. Therefore, there are at least two liars (the second and the third). Now, regardless of the first statement, it turns out that either he is right and, consequently, the fourth $\square$ is a knight, or he is wrong and the fourth is still a knight (since the knights were at the meeting). Thus, the one who remained silent is from the city of knights.

Answer: From the city of knights.