Notation Zeven_bool_succ := Z.even_succ (only parsing).Notation Zeven_bool_pred := Z.even_pred (only parsing).Notation Zodd_bool_succ := Z.odd_succ (only parsing).Notation Zodd_bool_pred := Z.odd_pred (only parsing).

Lemma Zsplit2 n : {p : Z * Z | let (x1, x2) := p in n = x1 + x2 /\ (x1 = x2 \/ x2 = x1 + 1)}.