proposition: Lemma cubic_ecpH : quasicubic (rev (cpring ecpH)).
proof: Proof. by apply: cubic_ecpN => //; apply cubic_ecpY. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap geometry color)