Find Peak Position in a Mountain Array

Consider an array nums to be a mountain array if it satisfies the following conditions:

• nums.length >= 3
• There exists an index 0 < j < nums.length - 1 such that nums[0] < nums[1] < ... < nums[j] and nums[j] > nums[j+1] > ... > nums[nums.length - 1]

Given an array that is guaranteed to be a mountain, find any index j that represents the peak element where the array first ascends and then descends.

Examples

Example 1:

Input: [1, 3, 2]
Output: 1

Example 2:

Input: [2, 5, 4, 1]
Output: 1

Constraints

• 3 ≤ nums.length ≤ 10000
• 0 ≤ nums[i] ≤ 100000
• nums is guaranteed to be a mountain array.