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

Q: ChKUlYUTQQBjZMZkgEed, lmQQBjZMZkgdEf

A: QQBjZMZkg
****
Q: hRVyvwHqnN, geHeyvwHqiBiYJ

A: yvwHq
****
Q: OmXpSbPR, NkdXpSbmO

A:
XpSb
****