MEMO 2018 I2
The two figures depicted below consisting of and unit squares, respectively, are called staircases. Consider a board consisting of cells, each being a unit square. Two arbitrary cells were removed from the same row of the board. Prove that the rest of the board cannot be cut (along the cell borders) into staircases (possibly rotated).
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Dataset text AI-MO AoPS. Quoted with source.
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