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

Example Input: KKebLWQCQzVIojj, nxQCQzVIopD
Example Output: QCQzVIo

Example Input: ilgSzrcUKLTNLJbMKMKSt, hFXIuUKLTNLJbMKWxSCkDjY
Example Output: UKLTNLJbMK

Example Input: Zhkcjb, ABkcFH
Example Output:
kc

