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

Example Input: nFgMXUzpStDAybiwm, aNJrXUzpStDjp
Example Output: XUzpStD

Example Input: XjYkMfARxWBSBjuXyDrFt, EtUxIfiHkMfARxWBSckTLTTnR
Example Output: kMfARxWBS

Example Input: jhZYoQNo, PaYZYoJK
Example Output:
ZYo