proposition: Lemma garea_subrect (r s : grect) : subpred r s -> (garea r <= garea s)%N.
proof: Proof. move=> srs; rewrite -!size_enum_grect uniq_leq_size ?enum_grect_uniq // => p. by rewrite !mem_enum_grect => /srs. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(div choice order ssralg ssrnum ssrint intdiv) fourcolor(hypermap)