instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
BfCCzPNLBbwCoxMVAG, vhwNLBbwCbH
answer:
NLBbwC


question:
KTAFonizDqCVvucpJWrItdw, rfFonizDqCVvYbGhb
answer:
FonizDqCVv


question:
DKbqJm, PRbqMf
answer:

bq