There was an old professor who started every class with a vulgar joke.

After a particularly nasty one, the women in the class decided to walk out the next time he started. The professor got wind of this, so the following day, he walked in and said, “Class, did you hear about the shortage of whores in India?” all the women stood up and headed for the door. “Wait, ladies!” cried the professor. “The boat doesn’t leave until tomorrow!”