instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
DGvUCrUVlUnQBShkWnfnceGasvI, NfzGUnQBShkWnpLMnY
answer:
UnQBShkWn


question:
ARGchkRez, kUwchkZPE
answer:
chk


question:
LERZAM, diRZbW
answer:

RZ