Definition Zeven_odd_dec n : {Zeven n} + {Zodd n}.Definition Zeven_dec n : {Zeven n} + {~ Zeven n}.Definition Zodd_dec n : {Zodd n} + {~ Zodd n}.

(* Specifications: *)
Lemma Zeven_not_Zodd n : Zeven n -> ~ Zodd n.
Lemma Zodd_not_Zeven n : Zodd n -> ~ Zeven n.
Lemma Zeven_Sn n : Zodd n -> Zeven (Z.succ n).
Lemma Zodd_Sn n : Zeven n -> Zodd (Z.succ n).
Lemma Zeven_pred n : Zodd n -> Zeven (Z.pred n).
Lemma Zodd_pred n : Zeven n -> Zodd (Z.pred n).