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[[http://bestcoder.hdu.edu.cn/contests/contest_showproblem.php?cid=889&pid=1007|题面]]

====简单题意====

房间是个 $n\times m$ 的网格，一共有 $k$ 个窗户，都在上下左右四条边上。在第 $0$ 时刻，每个窗户对应的格子上都会出现若干只蚊子。
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蚊子每个时刻可以往上下左右移动一格或者呆在原地不动。
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假设这些蚊子都足够聪明，请问最少花费多少时刻，使得所有格子上都有至少一只蚊子？
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蚊子在第 $0$ 时刻不能动。
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$n,m,k(1\leq n,m\leq 1000,1≤k≤6)$

====简单题解====
二分答案，把每个点映射到对应的 $2^k$ 状态节点中（容量$+1$），每个窗格往对应可达状态节点（$\text{该位}=1$）连边，网络流检验答案合法性。

@ws_zzyer 表示可以用霍尔定理替代网络流检验答案，待尝试！