instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
NNpkdhvgT, BMkAkdhvrwV
answer:
kdhv


question:
TnbLNKnNSs, NhDLNKnNRd
answer:
LNKnN


question:
iShkZCMrstWmlqBHaApVI, SxfeYYTmGZCMrstWmlqClf
answer:

ZCMrstWmlq