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: RtOkkgLvhgfGlX, vCOkgLvhzOa

A: kgLvh
****
Q: fJcwBbNIjzkBagh, hOTsRKNIjzkBin

A:
NIjzkB
****