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CF525D-Arthur and Walls

CF525D-Arthur and Walls 题目: 题目描述: Finally it is a day when Arthur has enough money for buying an apartment. He found a great option close to the center of the city with a nice price. Plan of the apartment found by Arthur looks like a rectangle $ n×m $ consisting of squares of size $ 1×1 $ . Each of

CF662B-Graph Coloring

CF662B-Graph Coloring 题目: 题目描述: You are given an undirected graph that consists of $ n $ vertices and $ m $ edges. Initially, each edge is colored either red or blue. Each turn a player picks a single vertex and switches the color of all edges incident to it. That is, all red edges with an endpoint in this vertex change the color to