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

Answer: SFj


Question: tWJoKSOAuVhmsomA, emdmnBFJoKSOAuVzSgW

Answer: JoKSOAuV


Question: QyhCxjDit, tgvCxjDLNIL

Answer:
CxjD