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

Example Input: lPhVhAQZWJDrvzcEaGEwKgZAuJI, qIJDrvzcEaGDRCRrB
Example Output: JDrvzcEaG

Example Input: LeHzcEFc, WFzcExvJ
Example Output: zcE

Example Input: PIwJeglkgZB, YgeglkMXg
Example Output:
eglk