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

Ex Input:
zBxuZfJgYrlRSzkmAktO, YNMgYrlRSzklmBOH

Ex Output:
gYrlRSzk


Ex Input:
pYmzRnGPQVPrqPApKTyvaO, tNGPQVPrqPVTh

Ex Output:
GPQVPrqP


Ex Input:
fEnMKYIRKgUWaPRpm, TqMSYIRKgUAHyZsK

Ex Output:

YIRKgU