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

Example Input: ykDpbd, YFDpmO
Example Output: Dp

Example Input: jexvmCmveGzFUimQMx, RVwOSJveGzFUimrcOwjEwe
Example Output: veGzFUim

Example Input: NzSENzHXDBIP, ezvxENzHXDBvUje
Example Output:
ENzHXDB