Let p be a prime number. There are p integers a0,…,ap−1 around a circle. In one move, it is allowed to select some integer k and replace the existing numbers via the operation ai↦ai−ai+k where indices are taken modulo p. Find all pairs of natural numbers (m,n) with n>1 such that for any initial set of p numbers, after performing any m moves, the resulting p numbers will all be divisible by n.Proposed by P. Kozhevnikov number theorymodular arithmetic