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

Example Input: GFhJafTV, waHhJaji
Example Output: hJa

Example Input: apGMPThLTCw, LvMPThYW
Example Output: MPTh

Example Input: zCZKKJGVLrizsfFct, fhzHLKJGVLripHo
Example Output:
KJGVLri