public class Solution
extends Object
668 - Kth Smallest Number in Multiplication Table\.
Hard
Nearly everyone has used the [Multiplication Table](https://en.wikipedia.org/wiki/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`