instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
aWshKwEuYBBdSwIAyXw, wfVuYBBdSwIAseTxR
answer:
uYBBdSwIA


question:
nXVXIEGP, fkXIEkU
answer:
XIE


question:
rvujvXFeiu, xPKsujvXdSb
answer:

ujvX