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11.6

Part of 1999 All-Russian Olympiad Regional Round

Problems(1)

4 colors in 50x50 square - All-Russian MO 1999 Regional (R4) 11.6

Source:

9/25/2024
The cells of a 50×5050\times 50 square are painted in four colors. Prove that there is a cell, on four sides of which (i.e. top, bottom, left and on the right) there are cells of the same color as it (not necessarily adjacent to this cell).
combinatoricsColoring