Given an integer array, return the kth smallest distance among all the pairs. The distance of a pair (A, B) is defined as the absolute difference between A and B.
Example 1:
Input: nums = [1,3,1] k = 1 Output: 0 Explanation: Here are all the pairs: (1,3) > 2 (1,1) > 0 (3,1) > 2 Then the 1st smallest distance pair is (1,1), and its distance is 0.
Note:

2 <= len(nums) <= 10000
. 
0 <= nums[i] < 1000000
. 
1 <= k <= len(nums) * (len(nums)  1) / 2
.