Definition jj : forall d : nat, mon d :=
  (fix jj (d : nat) : mon d :=
     match d as n return (mon n) with
     | O => n_0
     | S n => c_n n 0 (jj n)
     end).

(* Specifications: *)
Theorem jjProp1 : forall (d : nat) (m : mon d), d = 0 -> m = jj d.
Theorem jjProp2 : jj 0 = n_0.
Theorem monO_n0 : forall m : mon 0, m = n_0.
Lemma zRV_WR : WR (mon 0) (mdiv 0).