Definition. An f-graph is a directed graph where each vertex has outdegree 1. That is, each vertex has exactly one arrow coming out of it.

An f-graph is called epi if each vertex has indegree 1. That is, each vertex has exactly one arrow pointing to it. On a separate sheet of paper, draw an example of an epi f-graph and an example of a non-epi f-graph. Make a conjecture about the properties of epi f-graphs.