In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
--------
Question: spGRUmIYuGl, qkqRUmItqU

Answer: RUmI


Question: PQSFjlnU, kTSFjMUh

Answer: SFj


Question: cxYVucnmEQopeWHrPJ, jNnOaYVucnmEQoSE

Answer:
YVucnmEQo