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

[EX Q]: GoodBOwvrki, kRCsdBOwvrakgiH
[EX A]: dBOwvr

[EX Q]: aiqZheFuLtXAGRCGNBTAX, ssnVdztXAGRCGNBTIqmSJLZcy
[EX A]: tXAGRCGNBT

[EX Q]: PAgbIHQyEElUpIpmQW, zEElQyEElUpIpmKqrAwu
[EX A]:
QyEElUpIpm