4 people were imprisoned in different cages without any food or water. It is possible to get out of the top, but:
- Above the first cage there is a big flame.
- Above the second cage there is a huge and heavy stone.
- Above the third there is permanently boiling water.
- The cage number 4 is locked over top and bottom.
Moreover, all these locked cages hang over a deep ocean. Nearby there is a boat that you can reach by swimming. Those in the first 3 cages can escape through the bottom but they can't swim, while the fourth person can. By the way, the person in cage 3 can open the fourth cage because the key is in his cage.
You need to find a solution to save the lives of four prisoners.