Problem

Source: Kyiv City MO 2025 Round 1, Problem 8.2

Tags: combinatorics, grid



Is it possible to write positive integers from $1$ to $2025$ in the cells of a \( 45 \times 45 \) grid such that each number is used exactly once, and at the same time, each written number is either greater than all the numbers located in its side-adjacent cells or smaller than all the numbers located in its side-adjacent cells? Proposed by Anton Trygub