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

Example Input: OhMVLbQhBxEaOZY, iDVLbQhBxBiiD
Example Output: VLbQhBx

Example Input: UtUSmsOI, dCUSmGoQ
Example Output: USm

Example Input: PPQsnwXZhhbaMjaheJqk, gJFOaknwXZhhbaMZgn
Example Output:
nwXZhhbaM