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

Q: cUCQXEFSgRZjK, RYdvUQXEFSgRZVlwx

A: QXEFSgRZ
****
Q: pJqqIW, Ivqqxw

A: qq
****
Q: TgHQpfiPfIDRbQh, tevTpfiPfIiJrA

A:
pfiPfI
****