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

Example Input: jexvmCmveGzFUimQMx, RVwOSJveGzFUimrcOwjEwe
Example Output: veGzFUim

Example Input: BmxgSFWBlVX, kGgKrgSFWBlGunFcZ
Example Output: gSFWBl

Example Input: CwTYJWQbzEZkvcqKn, hBnhJWQbzEZkKmVM
Example Output:
JWQbzEZk