Suppose you have 5 football teams each team meets the other teams once. The total number of matches is 10. We may represent the results of these matches by a graph, in which if team A wins over team B, we draw an oriented arc from vertex A to vertex B. If team A ties with team B, we draw an undirected edge(or we do not draw any edge for simplicity). From the resulting graph, let P(A) be the number of points of the team A. P(A)=3 multiplied by the number of directed arcs out from A plus the number of undirected edges incident on A. Each graph in that manner represents the result of matches and vice versa. From the graph, we can arrange the teams. We can generalize this for n teams.