Let *G(V, E)* be an undirected graph, where each vertex in V corresponding to
a person who has published, the set of edges E consists of all un-ordered
pairs of vertices (u, v) such that the person corresponding to u and
the person corresponding to v are coauthors of at least one paper.
Let d(v) be the shortest path from v to the node corresponding to
Paul Erdos, measured by the number of edges on the path.
Then the person corresponding to node v has
Erdos number d(v).