Impossible.

Try to figure solve this, but don't cry when you can't figure it out.

A Russian war general oversees 24 captives. He decides to amuse himself by devising a game for the prisoners and promises to free them if they win. He sets up a room with a table and 2 drinking glasses: one on the left side of the table and one on the right side. The glasses can be turned to face up or down. He sends them individually into the room as often as he chooses and in any order. They are not allowed to make any marks other than turning only one of the 2 glasses; otherwise they are fed to the wolves. The captives are in single cells and have no indication of who has been in the room. They are also unaware of the glasses were originally up or down.
The general says that if one captive can tell him when all 24 have been in the room, he will free them. But if any one person guesses incorrectly, they are all thrown to the wolves. He allows them to consult the night before the game. They devise a plan to ensure success: how will they earn their freedom?

P.S. I'm pretty sure this one's not on the internet if you plan to google the answer (lame).

P.S.S. I have the distinguished honor of being an expert procrastinator in the truest sense of the title since I spent the last hour finding/revising this riddle.