proposition: Lemma leqD_dist m1 m2 m3 : `|m1 - m3| <= `|m1 - m2| + `|m2 - m3|.
proof: Proof. by rewrite -lez_nat PoszD !abszE ler_distD. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)