You are given an integer array `nums` and an integer `k`. Append `k` unique positive integers that do not appear in `nums` to `nums` such that the resulting total sum is minimum.

Return the sum of the `k` integers appended to `nums`.

Example 1:

    Input: nums = [1,4,25,10,25], k = 2
    Output: 5
    Explanation: The two unique positive integers that do not appear in nums which we append are 2 and 3.
    The resulting sum of nums is 1 + 4 + 25 + 10 + 25 + 2 + 3 = 70, which is the minimum.
    The sum of the two integers appended is 2 + 3 = 5, so we return 5.

Example 2:

    Input: nums = [5,6], k = 6
    Output: 25
    Explanation: The six unique positive integers that do not appear in nums which we append are 1, 2, 3, 4, 7, and 8.
    The resulting sum of nums is 5 + 6 + 1 + 2 + 3 + 4 + 7 + 8 = 36, which is the minimum.
    The sum of the six integers appended is 1 + 2 + 3 + 4 + 7 + 8 = 25, so we return 25.

Constraints:

- `1 <= nums.length <= 105`
- `1 <= nums[i] <= 109`
- `1 <= k <= 108`