In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.

Q: uHGHiARtdJbuG, OdZmiARtdrhC

A: iARtd
****
Q: vytthSjj, XVttthSFAvk

A: tthS
****
Q: xGPCvvow, vVPCvHS

A:
PCv
****