Let's call an array `arr` a mountain if the following properties hold:

- `arr.length >= 3`
- There exists some `i` with `0 < i < arr.length - 1` such that:
  - `arr[0] < arr[1] < ... arr[i-1] < arr[i]`
  - `arr[i] > arr[i+1] > ... > arr[arr.length - 1]`

Given an integer array `arr` that is guaranteed to be a mountain, return any `i` such that `arr[0] < arr[1] < ... arr[i - 1] < arr[i] > arr[i + 1] > ... > arr[arr.length - 1]`.

Example 1:

    Input: arr = [0,1,0]
    Output: 1

Example 2:

    Input: arr = [0,2,1,0]
    Output: 1

Example 3:

    Input: arr = [0,10,5,2]
    Output: 1

Constraints:

- `3 <= arr.length <= 104`
- `0 <= arr[i] <= 106`
- `arr` is guaranteed to be a mountain array.

Follow up: Finding the `O(n)` is straightforward, could you find an `O(log(n))` solution?