proposition: Lemma cface_ecpY u : cface ecpY u = (u \in [:: ecpY : ecpY; face ecpY]).
proof: Proof. exact: fconnect_cycle. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap geometry color)