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

Example Input: ZhHtTXaUmsQfUMNrnt, KvvebSXaUmsQfBspwM
Example Output: XaUmsQf

Example Input: jAinxmaQUrmu, jqeEnxmaQUrWlrEqW
Example Output: nxmaQUr

Example Input: kTCKDGmirFtIOFZySRHiqIRRGe, hfOSuCksiFtIOFZySRHJHrssnlkiF
Example Output:
FtIOFZySRH