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

Example Input: pIkAtJHVcvzzZVz, btWerNSHVcvzzZTz
Example Output: HVcvzzZ

Example Input: zfUPUDeKbCMQa, BkAJFJUDeKbCMZmkFu
Example Output: UDeKbCM

Example Input: oZodgFfqKCuqdyHY, uXUqKCuqdyUGh
Example Output:
qKCuqdy