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

Example Input: zgJGhxLU, EwJGhedW
Example Output: JGh

Example Input: GoodBOwvrki, kRCsdBOwvrakgiH
Example Output: dBOwvr

Example Input: ZFExHRiisswAfzTUxahgy, ZqsgUSRiisswAfzTENg
Example Output:
RiisswAfzT