You are one of 20 logicians worldwide to receive this letter. You don't know each other, but you all think alike. An address is given, and you are told that if a letter is received from one **and only one** of you, all 20 will equally split a large sum of money. If no letters are received, or more than one, no prize.

What would you to for a chance of winning the prize? What could you do in order to maximise the probability of winning?