1671. Minimum Number of Removals to Make Mountain Array
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You may recall that an array `arr` is a mountain array if and only if:

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

Given an integer array `nums`​​​, return the minimum number of elements to remove to make `nums​​​` a mountain array.

Example 1:

```Input: nums = [1,3,1]
Output: 0
Explanation: The array itself is a mountain array so we do not need to remove any elements.
```

Example 2:

```Input: nums = [2,1,1,5,6,2,3,1]
Output: 3
Explanation: One solution is to remove the elements at indices 0, 1, and 5, making the array nums = [1,5,6,3,1].
```

Constraints:

• `3 <= nums.length <= 1000`
• `1 <= nums[i] <= 109`
• It is guaranteed that you can make a mountain array out of `nums`.
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