Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
A graph that has an arbitrary number of negative loops, as many as the number of nodes in the second layer, but its PF-distance is 1: to avoid negative feedback, it suffices to switch the sign of the single (negative) arrow from the bottom to the top node. All unlabeled arrows are positive.
