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

[EX Q]: vMYfFo, EHYfnP
[EX A]: Yf

[EX Q]: HKqfdEvqDuGhWByFlzIEeYh, VVaZfkLCMuGhWByFlzIOZaXbMCA
[EX A]: uGhWByFlzI

[EX Q]: RusMOjSNznHpiBtJOtwyGyS, jVdMOjSNznHpilzrgHXF
[EX A]:
MOjSNznHpi