2008 OIM Problems/Problem 6

Problem

In a "biribol" match, two teams of four people each face each other. A biribol tournament is organized in which $n$ people participate, who form teams for each match (teams are not fixed). At the end of the tournament it was observed that every two people competed exactly one match on rival teams. For what values of $n$ is it possible to organize a tournament with such features?

~translated into English by Tomas Diaz. ~orders@tomasdiaz.com

Solution

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See also

OIM Problems and Solutions