ok!
There are two separate rooms. In the first one there are 3 lamps, in the secont the keys that turn these lamps on and off. You enter the second room (the one with the keys) and you are allowed to do anything that does not damage the keys. You know that all 3 are off when you enter. Then you must enter the room with the lamps and say which key is to which lamp. There is no visibility between both rooms.
How will you do it?
