In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
--------
Question: SFQHJlK, dHfQHJoUC

Answer: QHJ


Question: eMDNXl, ZZDNAa

Answer: DN


Question: kAYtEKdRxb, ewYtEKoM

Answer:
YtEK