Beyond the spectacle of the sky
time limit per test
2 seconds
memory limit per test
256 megabytes
You have a team of $N$ people. For a particular task, you can pick any non-empty subset of people. The cost of having $x$ people for the task is $x^k$.
Output the sum of costs over all non-empty subsets of people.
Time limit : 2sec / Memory limit : 256MB
题意：给$3N$个数，$3$个一组，我们取每个组第二大的数出来相加，问最大能够是多少
还是…还是弄个door吧。。
Time limit : 2sec / Memory limit : 256MB
We have $N$ pieces of ropes, numbered 1 through $N$. The length of piece $i$ is $a_i$.
At first, for each $i(1≤i≤N−1)$, piece $i$ and piece $i+1$ are tied at the ends, forming one long rope with $N-1$ knots. Snuke will try to untie all of the knots by performing the following operation repeatedly:
Is it possible to untie all of the $N−1$ knots by properly applying this operation? If the answer is positive, find one possible order to untie the knots.
DJL为了避免成为一只咸鱼，来找Johann学习怎么求最长公共子序列。
经过长时间的摸索和练习，DJL终于学会了怎么求LCS。Johann感觉DJL孺子可教，就给他布置了一个课后作业：
给定两个长度分别为$n$和$m$的序列，序列中的每个元素都是正整数。保证每个序列中的各个元素互不相同。求这两个序列的最长公共子序列的长度。
DJL最讨厌重复劳动，所以不想做那些做过的题。于是他找你来帮他做作业。