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====== A ======
签到，典型cf型脑经急转弯。然鹅题目样例已经把所有可能列光了qaq，特判2*2成立和长，寛有一个是1就成立，其余都不可能。
====== B ======
找规律+公式题，不难算出公式 第i个金字塔需要火柴棒数为 n(3*n+1)/2,之后列方程求解。注意开longlong 不然会爆
====== C ======
知道unrated前的最后一道题。简单数论题，将无穷长数列按每n个一段的规律分别移动，稳有没有重合和缺失。经过计算发现若移动后有重合，那么必定存在i，j ，使ai+i与aj+j模n同余，之后只要判断会不会冲突就好了。