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

QvtDqzQiSknPbRCG, hVxHdqzQiSknPbumdpNIf
qzQiSknPb

YPeBvuJXaSLLPhKpUQ, ryjPdyuJXaSLLPhIzBeJP
uJXaSLLPh

pZnkyiKysLvzVabfe, YQGmVlEikyiKysLvzVSYNR

kyiKysLvzV