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

Example Input: kWnjCoVmCSVuW, RILPKCoVmCSVbaOza
Example Output: CoVmCSV

Example Input: srPyjmTQhdFFMcQ, QQGBdtyjmTQhmfEy
Example Output: yjmTQh

Example Input: MepDjslH, koLDjsqs
Example Output:
Djs