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

[EX Q]: kUoqCMPFTqGE, guoqCMPkwJs
[EX A]: oqCMP

[EX Q]: pYmzRnGPQVPrqPApKTyvaO, tNGPQVPrqPVTh
[EX A]: GPQVPrqP

[EX Q]: KEZVzc, hrZVSd
[EX A]:
ZV