instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
SQNzngllNbOkKDK, MijfNzngllNDfWge
answer:
NzngllN


question:
rEHxRBOktYreNkK, NCOktYreFFCFwi
answer:
OktYre


question:
UKIUOpVBjHyQkBtF, sfrYBjHyQkBObXtkB
answer:

BjHyQkB