simple induction 1; intros; auto with arith pts.
inversion_clear H0; auto with arith pts.
inversion_clear H1.
apply iu_type.
apply le_trans with m; auto with arith pts.
Qed.

(* Specifications: *)
Lemma univ_inv :
forall s s' : srt_v6,
univ s s' -> forall P : Prop, (inv_univ s s' -> P) -> P.