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

[EX Q]: XjYkMfARxWBSBjuXyDrFt, EtUxIfiHkMfARxWBSckTLTTnR
[EX A]: kMfARxWBS

[EX Q]: fCGEhfHvcRouHzNw, gtjBkhfHvcRouHee
[EX A]: hfHvcRouH

[EX Q]: TnLspQrvLKkNMWNZw, OzHQmHJpQrvLKkNAGoNec
[EX A]:
pQrvLKkN