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: WTnsmP, INnsIM
Example Output: ns

Example Input: yJpIltQg, NqsIltXQn
Example Output:
Ilt