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

[EX Q]: HiEuutntEBpU, fdkqEuutntEBABdGZRND
[EX A]: EuutntEB

[EX Q]: yRhCObvPZYoKUoQnyaatR, NHzLJYPZYoKUoQnJnIsZxC
[EX A]: PZYoKUoQn

[EX Q]: hJpOTGHJB, TDbZpOTGHRPRT
[EX A]:
pOTGH