You and 24 other immortals have been captured and will each be imprisoned in a single room with no communication to each other. Each day, 1 person will be taken from there room and led to a central room that contains nothing but a working light and it's switch. There is no pattern or order to who is taken to the central room - the guards could choose to take the same person every day for 5 years if they want to. When someone is taken out, they do not see or hear any of the other prisoners.
The only way you will get out is if one of the prisoners correctly tells the guards that every prisoner has been in the room at least one time. If they are right, then all of the prisoners are released; but if they are wrong, then all of the prisoners are trapped there forever.
The night before everyone is put into their rooms, all of the prisoners can meet together without the presence of the guards. During this meeting, you and your fellow prisoners need to come up with a plan such that once every person has been in the room at least once, then one of you will be able to accurately inform the guards and release everyone. Your plan must be foolproof - you cannot afford to guess wrong.
What is the plan that will save you and your comrades?