Mountainous Palindromic Subarray

시간 제한2초메모리 제한2048 MB

요약

앞부분은 순증가, 뒷부분은 순감소하면서 앞뒤로 읽어도 같은 가장 긴 부분 배열의 길이를 구한다.

난이도: 보통10점 중 4점
유형: 투 포인터, 구현
정답자: 아직 제출이 없습니다

문제

An array is Mountainous if it is strictly increasing, then strictly decreasing. Note that Mountainous arrays must therefore be of length three or greater.

A Subarray is defined as an array that can be attained by deleting some prefix and suffix (possibly empty) from the original array.

An array or subarray is a Palindrome if it is the same sequence forwards and backwards.

Given an array of integers, compute the length of the longest Subarray that is both Mountainous and a Palindrome.

입력

The first line of input contains an integer $n$ ( $1 \le n \le 10^6$ ), which is the number of integers in the array.

Each of the next $n$ lines contains a single integer $x$ ( $1 \le x \le 10^9$ ). These values form the array. They are given in order.

출력

Output a single integer, which is the length of the longest Mountainous Palindromic Subarray, or $-1$ of no such array exists.

예제2

예제 1
입력
```
8
2
1
2
3
2
1
7
8
```
예상 출력
```
5
```
예제 2
입력
```
5
2
5
8
7
2
```
예상 출력
```
-1
```