instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
PShMbsbexXGlpBuMMDZZS, sVqGxSexXGlpBxuHXoI
answer:
exXGlpB


question:
skZGHS, HsZGge
answer:
ZG


question:
RRhvODSBUqUWKb, hHewxsDSBUqUWFz
answer:

DSBUqUW