TOT 2006 Fall - Senior O-Level p3 2006 x 2006 board
Source:
February 25, 2020
combinatorics
Problem Statement
Each of the numbers is placed at random into a cell of a 2006\times 2006 board. Prove that there exist two cells which share a common side or a common vertex such that the sum of the numbers in them is divisible by . (4)