proposition: Lemma arity_iter_face n x : arity (iter n face x) = arity x.
proof: Proof. by apply: arity_cface; rewrite cfaceC fconnect_iter. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap jordan)