MathDB
100 colors for 50x50 table, 1x2 tile related condition

Source: 2023 South Russian Girls MO - Assara Juniors p4 / M2774 in no. 11-12 of Kvant, 2023

February 28, 2024
combinatoricsColoring

Problem Statement

In a 50×5050 \times 50 checkered square, each cell is painted in one of 100100 given colors so that all colors are present and it is impossible to cut a single-color domino from the square (i.e. a 1×21 \times 2 rectangle). Galiia wants to recolor all the cells of one of the colors into another color (out of the given 100100 colors) so that this condition is preserved (i.e., it is still impossible to cut out a domino of the same color). Is it true that Galiia will definitely be able to do this?