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:
faHRBWyXsYzYmHQyy, aHTyXsYzYeXBFV
answer:
yXsYzY


question:
pBOeqWSpCDWwLw, oXoWSpCDWWv
answer:

WSpCDW