proposition: Lemma zvalid_fit pl pr : zvalid pl pr -> fitp x0 (catrev_part pl pr).
proof: Proof. move->; rewrite fitp_cat. by case/andP: fit_p0r => /eqP <-; rewrite /= (iter_face_arity x0) andbb. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap geometry part quiz quiztree)