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题库练习 Permutation

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A9471 | $Permutation$

时间限制1s

内存限制256MB

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题目描述

You are given a permutation of numbers from $1$ to $n$ . Determine whether there's a pair of integers $a,b$ $(1<=a,b<=n; a\neqb)$ such that the element ![](/uploads/acgo/image/caee7da493042589_2c4cb8541588.jpeg) (note, that it is usual division, not integer one) is between $a$ and $b$ in this permutation.

输入格式

First line consists of a single integer $n$ ( $1<=n<=300000$ ) — the size of permutation. Second line contains $n$ integers — the permutation itself.

输出格式

Print "YES", if such a pair exists, "NO" otherwise (in both cases without quotes, the answer is case insensitive).

输入输出样例

输入 #1

4
1 3 4 2

输出 #1

NO

输入 #2

5
1 5 2 4 3

输出 #2

YES

C++ 编辑器

输入

输出