proposition: Lemma gtouch_refl p : gtouch p p.
proof: Proof. by case: p => x y; rewrite /= !ger_addl !ltr_addl. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(div choice order ssralg ssrnum ssrint intdiv) fourcolor(hypermap)