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Problem 3, 2018

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A mathematical commission has \(2n\) members, where \(n \geqslant 3\). Every member of the commission is in a quarrel with exactly one other member (the relation is symmetric). In how many ways can the commission be divided into three committees - one for setting the problems, one for grading them, and one for organising the competition - so that each committee has at least two members, and no two members who are in a quarrel end up on the same committee?

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Serbian Municipal Competition 2018, high school grade I, category A, problem 3. Organized by the Mathematical Society of Serbia (DMS). Source