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

Example Input: ATmVEtUuZOgsBUuL, UMUuZOgsBPVT
Example Output: UuZOgsB

Example Input: FQAznAuFjoBKRKB, hPmtFFPnuAznAuFjoBKTgkeJyjcd
Example Output: AznAuFjoBK

Example Input: INyyovoQalkXPPacVGF, OBWfpQvoQalkXPPaTsZKnvB
Example Output:
voQalkXPPa