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: fdxgzAMP, xrcxgzYW
Example Output: xgz

Example Input: xIDCtTifywHZetd, izDMTifywFfv
Example Output:
Tifyw