Four men set foot in the desert. Suddenly all four are knocked out at the same time. They woke up and buried their heads in sand that could only be seen straight ahead. They are arranged so that each person looks at the head of the other in front of him. However, there is a separation barrier between the first person and the second person. Therefore, the first person sees only the desert. The second man can only see the wall. The third man looks at someone else's head and wall. The fourth man looks at the two heads and the wall. There is a hat on each man's head. The underside of each cap is black, while the outside of each cap is blue or white. Before any of the men can speak, their prisoners tell them if they speak, they die. But if any of them can guess the color of their hat on the first attempt, they will be free. POWs say they have two blue hats and two white hats. Observing the situation omnisciently, we know that the order of the caps is blue, white, blue, white. So, knowing each person's point of view in the sand, they know that they can only see the color of the hat / wall / desert in front of them, which of the four men himself I certainly know the color of the hat. Why is it even more important?
