A professor goes along the corridor of the college. A student approaches him: Good morning, professor. May I ask you? Sure. Tell me, please, when you go to bed where do you put your beard on or under the cover? After some pause: Well, you know, I don't remember... Well, sorry. In a one week the exhausted green professor with red eyes meets the same student and cries: You, I can't sleep for the whole week! It is uncomfortable to sleep in both positions!