Two-side grid with numbers
Source: St. Petersburg 2023 9.4=10.4
August 12, 2023
combinatorics
Problem Statement
One side of a square sheet of paper is colored red, the other - in blue. On both sides, the sheet is divided into identical square cells. In each of these cells is written a number from to . Find the smallest ,for which the following properties hold simultaneously:
(i) on the red side, any two numbers in different rows are distinct;
(ii) on the blue side, any two numbers in different columns are different;
(iii) for each of the squares of the partition, the number on the blue side is not equal to the number on the red side.