instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
XwBMFIV, SNLBMFZQ
answer:
BMF


question:
LJJvLTK, jpFJvLqh
answer:
JvL


question:
baBRvlmcoyRjW, uCzvlmcoyRMPT
answer:

vlmcoyR