5 colors for checkered plane - All-Russian MO 1999 Regional (R4) 9.5
Source:
September 25, 2024
combinatoricscombinatorial geometrytiles
Problem Statement
All cells of the checkered plane are painted in colors so that in any figure of the species https://cdn.artofproblemsolving.com/attachments/f/f/49b8d6db20a7e9cca7420e4b51112656e37e81.png all colors are different. Prove that in any figure of the species \begin{tabular}{ | l | c| c | c | r| } \hline & & & &\\ \hline \end{tabular}, all colors are different..