Question 63
We say that a group of $25$ students is a *team* if any two students in this group are friends. It is known that in the school every student belongs to at least one team, but if any two students end their friendship, then at least one student does not belong to any team. We say that a team is *special* if at least one student of the team has no friend outside this team. Show that any two friends belong to some special team.