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: QqtCFzXHPNFXx, XECFzXHPSGwUuk
Example Output: CFzXHP

Example Input: NUzbRmzbfLGjJedtO, BMzbfLGjJIEr
Example Output:
zbfLGjJ