Mountainous Palindromic Subarray
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.
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.
Output a single integer, which is the length of the longest Mountainous Palindromic Subarray, or $-1$ of no such array exists.
|Sample Input 1||Sample Output 1|
8 2 1 2 3 2 1 7 8
|Sample Input 2||Sample Output 2|
5 2 5 8 7 2