ASU 456 All Soviet Union MO 1987 9 or 10 of 33 knights in night guard
Source:
August 7, 2019
combinatoricsalgebra
Problem Statement
Every evening uncle Chernomor (see Pushkin's tales) appoints either or of his 33 "knights" in the "night guard". When it can happen, for the first time, that every knight has been on duty the same number of times?