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:
IobjElBjKvpepE, kRulBjKvvxU
answer:
lBjKv


question:
NgPFdVIkAHLbC, MocKRVIkAHPqkZp
answer:

VIkAH