Nearly everyone has used the Multiplication Table. The multiplication table of size `m x n` is an integer matrix `mat` where `mat[i][j] == i * j` (1-indexed).

Given three integers `m`, `n`, and `k`, return the `kth` smallest element in the `m x n` multiplication table.

Example 1:

    Input: m = 3, n = 3, k = 5
    Output: 3
    Explanation: The 5th smallest number is 3.

Example 2:

    Input: m = 2, n = 3, k = 6
    Output: 6
    Explanation: The 6th smallest number is 6.

Constraints:

- `1 <= m, n <= 3 * 104`
- `1 <= k <= m * n`