simple induction 1; auto with arith pts.
simple destruct x; simpl in |- *; intros.
inversion_clear H0; simpl in |- *; auto with arith pts.
elim sort_norm with e s y; auto with arith pts.
elim H1.
elim H1.
elim H1.
elim H1.
Qed.

Lemma sort_is_norm : forall (e : env) (t : term), is_sort t -> normal R e t.
simple destruct t; simpl in |- *; auto with arith pts; intros; elim H.