Young people must open five doors in turn, and a tiger will go out and appear in one of them. Young people can get the princess if they kill the tiger. Then the young man stood in front of the door and began to reason. If there is no tiger after I open the first four doors, the tiger must be at the fifth door. The king says the tiger is at an unexpected door, so the tiger is definitely not at the fifth door. By analogy, tigers do not exist. Finally, the young man rashly began to push the door, and the tiger jumped out of the second door.