proposition: Lemma rotr_face n (s : seq G) : sface s -> sface (rotr n s).
proof: Proof. exact: rot_face. Qed.
imports: mathcomp(all_ssreflect) fourcolor(hypermap geometry color coloring walkup combinatorial4ct cfmap) GraphTheory(edone preliminaries bij digraph sgraph) GraphTheory(connectivity minor hmap_ops smerge hcycle arc)