Andy’s birthday party has just been moved up by a week. All the toys in Andy’s room are worried about being replaced by fancy new toys. Sheriff Woody, Andy’s favourite toy, and the others are waiting for the party to get over and meet the new toys.
At the party, Andy’s mother hosts a game. Since not everyone got Andy a present, she removes the name tags from all the gifts, so all 121 of Andy’s friends either lie or tell the truth about getting Andy a gift. The game consists of each of the 122 children (121 friends, plus Andy) shaking hands with each other child. After hands are shaken, Andy’s mom asks each person "How many truth-tellers did you shake hands with?" Each child gave a different answer ranging from 0 to 121. Andy must answer the number of liars in the party to get a surprise gift. What should Andy's answer be?