Given an integer array arr, return the length of the longest contiguous subarray that forms a mountain.

A subarray arr[l..r] is a mountain if all of the following are true:
A mountain has length at least $3$.
There exists an index p with l < p < r such that arr[l] < arr[l+1] < ... < arr[p] and arr[p] > arr[p+1] > ... > arr[r].
In other words, the values strictly increase up to a single peak, then strictly decrease after the peak.

If no mountain exists in arr, return $0$.

Note: Consider whether you can solve this in a single pass using $O(1)$ extra space.

Constraints:

• $1 \leq$ arr.length $\leq 10^4$

• $0 \leq$ arr[i] $\leq 10^4$

Input: arr = [2,1,4,7,3,2,5]-List[int]
Output: 5-int
Explanation: The longest mountain is [1,4,7,3,2] (strictly increasing to peak 7, then strictly decreasing), and its length is 5.

Input: arr = [2,2,2]-List[int]
Output: 0-int
Explanation: A mountain requires a strict increase followed by a strict decrease. With all values equal, no mountain exists.

Input: arr = [0,1,2,3,4,5,4,3,2,1,0]-List[int]
Output: 11-int
Explanation: The entire array is a mountain: it strictly increases from 0 to peak 5, then strictly decreases back to 0, for a length of 11.

Input: arr = [1,3,2]-List[int]
Output: 3-int
Explanation: This is the smallest possible mountain (length 3): it increases 1 -> 3, then decreases 3 -> 2.

Input: arr = [1,2,3,4,5]-List[int]
Output: 0-int
Explanation: The array only increases and never decreases, so it cannot form a mountain.

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