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

Example Input: DQVkAbWTTPhoBx, TeWTTPhonxcIKL
Example Output: WTTPho

Example Input: mmDhYqPJC, qThYqxW
Example Output: hYq

Example Input: bTYwEMZrx, GnvwEMZyWE
Example Output:
wEMZ