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

Example Input: HSsyZzZLZAAq, MFEZzZLJC
Example Output: ZzZL

Example Input: zfUPUDeKbCMQa, BkAJFJUDeKbCMZmkFu
Example Output: UDeKbCM

Example Input: XdJVnL, AOJVRo
Example Output:
JV

