proposition: Lemma le_sig1 : {homo sig1 : i j / i <= j}.
proof: Proof. by move=> i j; rewrite /sig1/= -le_sig leEsig/=; case: leP. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)