proposition: Lemma closedF_ecpU : fclosed face (predC1 (ecpU : ecpU)).
proof: Proof. by move=> u _ /=/eqP <-; rewrite !inE -!cface_ecpU -cface1r. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap geometry color)