proposition: Lemma lt_sig : {mono sig : i j / i < j}.
proof: Proof. by move=> i j; rewrite !ltNge le_sig. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)