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1965 All Russian Mathematical Olympiad
061
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1965 All Russian Mathematical Olympiad
Problems
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ASU 061 All Russian MO 1965 100 men help the police, 3 every evening
Source:
6/19/2019
A society created in the help to the police contains
100
100
100
men exactly. Every evening
3
3
3
men are on duty. Prove that you can not organise duties in such a way, that every couple will meet on duty once exactly.
combinatorics