instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
rlBoVyFsYqpmmQmelGBg, iKKaIyFsYqpmmWcrKn
answer:
yFsYqpmm


question:
yQCDWefwvrPP, RwoMDWefwhSxTR
answer:
DWefw


question:
OlfhHGbkrTz, nBfhHGbVqKqX
answer:

fhHGb