This is a variation of an old puzzle.
The game starts with several people sitting in a circle, everyone facing the back of another person. They are all wearing blind folds, so nobody can see anyone else. In particular, nobody can see how many people are there in total.
One of them is the leader. They win the game if the leader figures out the exact number of people in the circle.
They are only allowed to communicate with each other under the following rules:
- When the game starts, the leader is allowed to touch the person in front of him.
- After that, a person who is touched by another person is allowed to touch the person in front of him.
- Whenever a person touches another person once, he is not allowed to touch anymore, until he himself is touched again.
- Every touch can be either on the left shoulder or on the right shoulder, but should contain no more information than "left or right" (e.g. small gestures/knocks/touch power/which hand touches/etc. are all IRRELEVANT).
- Other than the touch as specified above, no communication is allowed.
As usual, before the game starts they are allowed to agree on a strategy. What strategy can they use to win the game?
This is a logical puzzle and not lateral thinking.
It's also impossible to know the number of people when they discuss the strategy: it could happen that only part of them are selected to participate in the game.