A knight remembers a banquet that he had:
"Oh, that was a really nice banquet; all the liars and the knights of the kingdom were there, even the village fool. We all ate and drank and at the end of it the king asked each one of us to make a statement about someone else, I mean, to say if he is a liar or a knight. finaly, one statement was said about each one of us, and every one made the same statement except for the village fool who made a different statement. By the way, can you tell me how many people were in the banquet?"
"No", you say, "but I can tell you something else about the NUMBER of people that were in the banquet."
What can you tell? What statement did each one of the participants make?