intros.
inversion_clear H.
Inversion_typ H0.
left with s2; trivial with arith pts.
Qed.

(* Specifications: *)
Theorem wf_type_subst :
forall (e : env) (v V T : term),
wf_type (Ax V :: e) T -> typ e v V -> wf_type e (subst v T).
Theorem wf_type_subst :
forall (e : env) (v V T : term),
wf_type (Ax V :: e) T -> typ e v V -> wf_type e (subst v T).