In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.

Example Input: OgWFOfjNYmXVjBBvOdunIc, eGljKGnzFKFOfjNYmXVjdlqsT
Example Output: FOfjNYmXVj

Example Input: uHGHiARtdJbuG, OdZmiARtdrhC
Example Output: iARtd

Example Input: oAWTXMjMitgPHGxc, LYOjMitgPHgxI
Example Output:
jMitgPH