CF985C Liebig's Barrels

你有一共m=n*k个木板。第i个木板的长度为ai。你必须用其中的每k条木板组成n个木桶。每条木板只能且必须属于一个木桶。我们把第j个木桶的最短的木板长度作为这个木桶的容积vj 你想要让这组合起来的n个木桶总容积最大。但是你需要让他们的容积尽量差不多，使得无论那两个木桶的容积差不超过l，即|vx-vy|

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In the first example you can form the following barrels: $ [1,2] $ , $ [2,2] $ , $ [2,3] $ , $ [2,3] $ . In the second example you can form the following barrels: $ [10] $ , $ [10] $ . In the third example you can form the following barrels: $ [2,5] $ . In the fourth example difference between volumes of barrels in any partition is at least $ 2 $ so it is impossible to make barrels equal enough.