IMO Shortlist 2002 problem C7
Dodao/la:
arhiva2. travnja 2012. Among a group of 120 people, some pairs are friends. A weak quartet is a set of four people containing exactly one pair of friends. What is the maximum possible number of weak quartets ?
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Among a group of 120 people, some pairs are friends. A weak quartet is a set of four people containing exactly one pair of friends. What is the maximum possible number of weak quartets ?
Izvor: Međunarodna matematička olimpijada, shortlist 2002
Školjka 
