You are given two integer arrays `nums1` and `nums2` sorted in ascending order and an integer `k`.

Define a pair `(u, v)` which consists of one element from the first array and one element from the second array.

Return the `k` pairs `(u1, v1), (u2, v2), ..., (uk, vk)` with the smallest sums.

Example 1:

    Input: nums1 = [1,7,11], nums2 = [2,4,6], k = 3
    Output: [[1,2],[1,4],[1,6]]
    Explanation: The first 3 pairs are returned from the sequence: [1,2],[1,4],[1,6],[7,2],[7,4],[11,2],[7,6],[11,4],[11,6]

Example 2:

    Input: nums1 = [1,1,2], nums2 = [1,2,3], k = 2
    Output: [[1,1],[1,1]]
    Explanation: The first 2 pairs are returned from the sequence: [1,1],[1,1],[1,2],[2,1],[1,2],[2,2],[1,3],[1,3],[2,3]

Example 3:

    Input: nums1 = [1,2], nums2 = [3], k = 3
    Output: [[1,3],[2,3]]
    Explanation: All possible pairs are returned from the sequence: [1,3],[2,3]

Constraints:

- `1 <= nums1.length, nums2.length <= 105`
- `-109 <= nums1[i], nums2[i] <= 109`
- `nums1` and `nums2` both are sorted in ascending order.
- `1 <= k <= 104`