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

Example Input: rvLoiycpZw, idcvoiycpcLyD
Example Output: oiycp

Example Input: hVQJkZyKfPoOQEukfAbXDpB, qpojyxWkZyKfPoOQEZkUI
Example Output: kZyKfPoOQE

Example Input: oCtWZYdkvZ, pkktWZYdEHMW
Example Output:
tWZYd