proposition: Lemma size_walkqz x qz : size (walkqz x qz) = size (flatqz qz).
proof: Proof. by case: qz => q0 q1 /=; rewrite /= !size_cat !size_walkq. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap geometry coloring)