Nearly everyone has used the Multiplication Table. The multiplication table of size
m x n is an integer matrix
mat[i][j] == i * j (1-indexed).
Given three integers
k, return the
kth smallest element in the
m x n multiplication table.
Input: m = 3, n = 3, k = 5 Output: 3 Explanation: The 5th smallest number is 3.
Input: m = 2, n = 3, k = 6 Output: 6 Explanation: The 6th smallest number is 6.
1 <= m, n <= 3 * 104
1 <= k <= m * n