We define a harmonious array as an array where the difference between its maximum value and its minimum value is exactly `1`.

Given an integer array `nums`, return the length of its longest harmonious subsequence among all its possible subsequences.

A subsequence of array is a sequence that can be derived from the array by deleting some or no elements without changing the order of the remaining elements.

Example 1:

    Input: nums = [1,3,2,2,5,2,3,7]
    Output: 5
    Explanation: The longest harmonious subsequence is [3,2,2,2,3].

Example 2:

    Input: nums = [1,2,3,4]
    Output: 2

Example 3:

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

Constraints:

- `1 <= nums.length <= 2 * 104`
- `-109 <= nums[i] <= 109`