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

Example Input: xzMUdHcoYJFWLOILjrg, vCscoYJFWLzO
Example Output: coYJFWL

Example Input: kIBDjQLEZepVNHqnKqhine, hTZepVNHqnYTajyzv
Example Output: ZepVNHqn

Example Input: dAMNsRajBvYr, csNsRajBvcY
Example Output:
NsRajBv