2001 IMO Shortlist Problems/C3
Problem
Define a -clique to be a set of people such that every pair of them are acquainted with each other. At a certain party, every pair of 3-cliques has at least one person in common, and there are no 5-cliques. Prove that there are two or fewer people at the party whose departure leaves no 3-clique remaining.
Solution
This problem needs a solution. If you have a solution for it, please help us out by adding it.