proposition: Lemma subitvP i1 i2 : i1 <= i2 -> {subset i1 <= i2}.
proof: Proof. by move=> ? ? /le_trans; exact. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(div fintype bigop order ssralg finset fingroup) mathcomp(ssrnum)