CF547D Mike and Fish

As everyone knows, bears love fish. But Mike is a strange bear; He hates fish! The even more strange thing about him is he has an infinite number of blue and red fish. He has marked $ n $ distinct points in the plane. $ i $ -th point is point $ (x_{i},y_{i}) $ . He wants to put exactly one fish in each of these points such that the difference between the number of red fish and the blue fish on each horizontal or vertical line is at most 1. He can't find a way to perform that! Please help him.

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