instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
KKrCLvJKRoyV, WDeLvJKCBdS
answer:
LvJK


question:
ptVlCwpfOZIi, QEdyVlCwpfOwp
answer:
VlCwpfO


question:
NHKnGrdqBEJh, vNEhIlKnGrdqBEncPoyVb
answer:

KnGrdqBE