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

Example Input: jdLbZSCzaAHGbNwILGmudOH, RdIPuEYJvUZSCzaAHGbNduLToRC
Example Output: ZSCzaAHGbN

Example Input: vMsEJRoLkWcmkuwNRz, ZmoLkWcmVZiBv
Example Output: oLkWcm

Example Input: aIZIsqL, wxSZIsEnO
Example Output:
ZIs