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You are given a string S consisting of only lowercase english letters and some queries.

You are given an array a1,a2,...,an(∀i∈[1,n],1≤ai≤n). Initially, each element of the array is unique.

这篇文章主要用于记录在探索评测系统Reef期间我所学的东西,以便之后查阅.

n个有标号的球围成一个圈。每个球有两种颜色可以选择黑或白染色。问有多少种方案使得没有出现连续白球7个或连续黑球7个。

对于可以离线的区间询问问题，莫队算法提出了一种可以在(无修改)，(带修改)内得出答案的方法。

zz6d likes reading very much, so he bought a lot of books. One day, zz6d brought n books to a classroom in school. The books of zz6d is so popular that...

Farmer John keeps a website called ‘FansBlog’ .Everyday , there are many people visited this blog.One day, he find the visits has reached P , which is...