IMO Shortlist 1990 problem 2


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2. travnja 2012.
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Given n countries with three representatives each, m committees A(1),A(2), \ldots, A(m) are called a cycle if

(i) each committee has n members, one from each country;
(ii) no two committees have the same membership;
(iii) for i = 1, 2, \ldots,m, committee A(i) and committee A(i + 1) have no member in common, where A(m + 1) denotes A(1);
(iv) if 1 < |i - j| < m - 1, then committees A(i) and A(j) have at least one member in common.

Is it possible to have a cycle of 1990 committees with 11 countries?
Izvor: Međunarodna matematička olimpijada, shortlist 1990