Please solve the programming task below using a self-contained code snippet in a markdown code block.

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.
 
Please complete the following python code precisely:
```python
class Solution:
    def findKthNumber(self, m: int, n: int, k: int) -> int:
```