You are given an integer array `nums`​​​ and an integer `k`. You are asked to distribute this array into `k` subsets of equal size such that there are no two equal elements in the same subset.

A subset's incompatibility is the difference between the maximum and minimum elements in that array.

Return the minimum possible sum of incompatibilities of the `k` subsets after distributing the array optimally, or return `-1` if it is not possible.

A subset is a group integers that appear in the array with no particular order.

Example 1:

    Input: nums = [1,2,1,4], k = 2
    Output: 4
    Explanation: The optimal distribution of subsets is [1,2] and [1,4].
    The incompatibility is (2-1) + (4-1) = 4.
    Note that [1,1] and [2,4] would result in a smaller sum, but the first subset contains 2 equal elements.

Example 2:

    Input: nums = [6,3,8,1,3,1,2,2], k = 4
    Output: 6
    Explanation: The optimal distribution of subsets is [1,2], [2,3], [6,8], and [1,3].
    The incompatibility is (2-1) + (3-2) + (8-6) + (3-1) = 6.

Example 3:

    Input: nums = [5,3,3,6,3,3], k = 3
    Output: -1
    Explanation: It is impossible to distribute nums into 3 subsets where no two elements are equal in the same subset.

Constraints:

- `1 <= k <= nums.length <= 16`
- `nums.length` is divisible by `k`
- `1 <= nums[i] <= nums.length`