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

Example Input: mJoHBJehHtkFS, ZMrDxHBJehHtxS
Example Output: HBJehHt

Example Input: UTdardKNThdYrGKMqZPeg, mvrThdYrGKMlcCxBtak
Example Output: ThdYrGKM

Example Input: ILzqZLaAuLLQpFJt, HXCwFZLaAuLIXLji
Example Output:
ZLaAuL