A female teacher walked into the class and saw a giant penis realistically depicted on the black board. Who did it? she asked. Silence. I demand that those who did it admit it! Silence. The last time, who did it? You won, it was me, Peter said from the last row. Now everybody shall leave the room except for Peter, the teacher said. The students walked out. Minute passed. Then five, then ten... After half an hour, Peter walked out, and, zipping up his fly, said, The main thing is advertisement.