A bunch of men are on an island A genie comes down and gathers everyone together and places a magical hat on some peoples heads (i e , at least one person has a hat) The hat is magical: it can be seen by other people, but not by the wearer of the hat himself To remove the hat, those (and only those who have a hat) must dunk themselves underwater at exactly midnight. If there are n people and c hats, how long does it take the men to remove the hats? The men cannot tell each other (in any way) that they have a hat.
FOLLOW UP:
Prove that your solution is correct.