instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
YRLHFm, odLHCI
answer:
LH


question:
zeuyZKwvIOfx, BlmZKwvspUt
answer:
ZKwv


question:
znQCmhLGZXVsOI, BRZamhLGZEEhF
answer:

mhLGZ