Just h-index

题号：NC52893
时间限制：C/C++/Rust/Pascal 1秒，其他语言2秒
空间限制：C/C++/Rust/Pascal 128 M，其他语言256 M
Special Judge, 64bit IO Format: %lld

题目描述

The h-index of an author is the largest h where he has at least h papers with citations not less than h.
Bobo has published n papers with citations $a_1, a_2, \dots, a_n$ respectively.
One day, he raises q questions. The i-th question is described by two integers $l_i$ and $r_i$ , asking the h-index of Bobo if has *only* published papers with citations $a_{l_i}, a_{l_i + 1}, \dots, a_{r_i}$ .

输入描述:

The input consists of several test cases and is terminated by end-of-file.
The first line of each test case contains two integers n and q.
The second line contains n integers .
The i-th of last q lines contains two integers  and .

输出描述:

For each question, print an integer which denotes the answer.

示例1

输入

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输出

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备注:

* 
* 
* 
* The sum of n does not exceed 250,000.
* The sum of q does not exceed 250,000.