proposition: Lemma refine_inset r : refine_rect (inset r) = inset (inset (refine_rect r)).
proof: Proof. by case: r => x0 x1 y0 y1 /=; rewrite !mulrnDl !addrA. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(div choice order ssralg ssrnum ssrint intdiv) fourcolor(hypermap)