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

DnAzbgMtdPKsNCMpBfc, QdfXRkWREzbgMtdPKsGx
zbgMtdPKs

yOGvgtAmwMwcIRtJ, cQtAmwMwcIRjfjO
tAmwMwcIR

xfZYYDKEqoRRu, ztCeYYDKEqoPG

YYDKEqo