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

Example Input: sHndIbPaygfNvnquxIHeteW, huLmJWXZIgfNvnquxIViQDhbuoL
Example Output: gfNvnquxI

Example Input: ZRjPgqbLL, uIsmPgqbBB
Example Output: Pgqb

Example Input: iqtcJeMenxb, jZJeMenyj
Example Output:
JeMen