instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
UtUSmsOI, dCUSmGoQ
answer:
USm


question:
nxTtNYaazlOyEBApiUSJS, BLazlOyEBCV
answer:
azlOyEB


question:
qzhoMbiefS, rcGhoMbBQFd
answer:

hoMb