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]: PShMbsbexXGlpBuMMDZZS, sVqGxSexXGlpBxuHXoI
[EX A]: exXGlpB

[EX Q]: zBrfEZux, BQimrfEZQFX
[EX A]:
rfEZ