Zebra Exercises, 2018-2019, Exercise 1

• Question 1

  Given an infinite grid whose vertices are colored with two colors, blue and red. Prove that there exist two horizontal lines and two vertical lines such that their four intersection points are colored with the same color.

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  Topics:

  Combinatorics -> Pigeonhole Principle Combinatorics -> Combinatorial Geometry Geometry -> Plane Geometry Combinatorics -> Colorings