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

Q: cKsJcqYvZO, UrsJcqBC

A: sJcq
****
Q: Owbiay, exbime

A: bi
****
Q: OKQWYoCWSfb, ycvWYoCuXcP

A:
WYoC
****