100 people are each assigned a number between 1 and 100 with repetitions (e.g. all of them may be assigned the number 17). Each of them sees all the numbers assigned to all the other 99, but none of them sees the number assigned to themselves.

Each of them needs to guess their own number (of course no information is exchanged between them - no one hears what others have guessed etc.).

What strategy can they employ in order to make sure that at least one of them guesses correctly?

Some Followup Thoughts

• Can they make sure that more than one person succeeds?
• How many different solutions to the riddle are there (i.e. how many strategies can the men employ?).