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

Example Input: HorIyjpfBFmKZQUIEoP, AcWOaOgVPmyjpfBFmKZQPFYiI
Example Output: yjpfBFmKZQ

Example Input: UZbmGVDzIaf, qfHwqGVDzIsd
Example Output: GVDzI

Example Input: qTCpbfooMqabISWbg, dldeSqYyooMqabISWLqoaZM
Example Output:
ooMqabISW