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

[EX Q]: STvKOHq, XMGvKOdyM
[EX A]: vKO

[EX Q]: fWJdaAfOCfejXZvidHM, gOpfOCfejXZbtLvSLZI
[EX A]: fOCfejXZ

[EX Q]: qiBcyAmQOXQ, FvyyAmQoqWV
[EX A]:
yAmQ