intros; elim p.
exact (Zrec2 P H).
intros; apply Zrec3; trivial with arith.
Qed.

(* Specifications: *)
(************)
Theorem recZ :
forall P : Z -> Set,
(forall n : Z, (forall m : Z, lt_absZ m n -> P m) -> P n) ->
forall p : Z, P p.