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

[EX Q]: zfUPUDeKbCMQa, BkAJFJUDeKbCMZmkFu
[EX A]: UDeKbCM

[EX Q]: QjDQjzAIsnYgNmmetl, vyqDQjzAIsnNajYEheP
[EX A]: DQjzAIsn

[EX Q]: TYBCUyQKBuZMsJU, bdCUyQKBuZyNCfqb
[EX A]:
CUyQKBuZ