The game is as follows:
Your three friends are led into one room and you are led into an adjoining room, where you can hear but not see your friends. You are sitting in front of a mirror; your friends are sitting in a circle with no mirrors, but where they can see each other. The prison warden shows you five small stickers, three black and two white. All four of you are blindfolded. He puts one sticker on your forehead and one on each of your friends' foreheads. Then he announces the rules:
"Absolutely no speaking or other communication is allowed, except to answer 'black' or 'white'. You are not allowed to move, except as much as required to speak the answer. I will remove the blindfolds from the three who are together. Any one of the three who tells me the color of the sticker on his own forehead wins, and you all go free. If any one says the wrong color, you will be executed. The three have five seconds for one of them to tell me the color of his (or her) own forehead sticker."
"If the three say nothing for five seconds, then I will remove the blindfold from the fourth [which is you]. The fourth then has thirty seconds to tell me the color of the sticker I kept."
The blindfolds of the three are removed. You hear nothing for five seconds. Then your own blindfold is removed, and you see in the mirror that you have a black sticker on your own forehead.
What do you say?
[Edited for clarity]