Four prisoners, 1, 2, 3 and 4, are all condemned to death. One of them is at random selected to be pardoned.
1 asks the guard who will be executed. The guard refuses to tell him so instead 1 says
'If 2 is to be pardoned tell me 3's name. If 3 is to be pardoned tell me 4's name. If 4 is to be pardoned tell me 2's name. If I am to be pardoned, roll a fair six-sided die, and if the number is one or two tell me 2's name, if the number is three or four tell me 3's name and if the number is five or six tell me 4's name.'
The guard comes back the next day and tells him 2's name.
What are the chances of each prisoner's survival now?