MathDB
Everything 0 mod 2023

Source: JOM 2023 P5

February 20, 2023
combinatorics

Problem Statement

Given a m×nm \times n rectangle where m,n2023m,n\geq 2023. The square in the ii-th row and jj-th column is filled with the number i+ji+j for 1im,1jn1\leq i \leq m, 1\leq j \leq n. In each move, Alice can pick a 2023×20232023 \times 2023 subrectangle and add 11 to each number in it. Alice wins if all the numbers are multiples of 20232023 after a finite number of moves. For which pairs (m,n)(m,n) can Alice win?
Proposed by Boon Qing Hong