Codeforces Round #524 (Div. 2) D - Olya and magical square

本文大部分思路转载自http://www.cnblogs.com/zquzjx/p/10014496.html，本人稍有改动 Recently, Olya received a magical square with the size of 2n×2n2n×2n. It seems to her sister that one square is boring. Therefore, she as

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