board 100x100 with mallest possible number of different residues modulo 33
Source: Rioplatense Olympiad 2012 level 3 P6
September 4, 2018
number theoryboardcombinatorics
Problem Statement
In each square of a board there is written an integer. The allowed operation is to choose four squares that form the figure or any of its reflections or rotations, and add to each of the four numbers. The aim is, through operations allowed, achieving a board with the smallest possible number of different residues modulo . What is the minimum number that can be achieved with certainty?