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

[EX Q]: wNiHcaiUPHnjp, aSTmjcaiUPHFzOu
[EX A]: caiUPH

[EX Q]: NTINFnRckGsfLqhSoA, UUONcKKFnRckGsfLqVak
[EX A]: FnRckGsfLq

[EX Q]: YbYHXq, ZkYHZu
[EX A]:
YH