intros p0 H'; red in |- *; intros H'0; discriminate.
intros p0; rewrite ZL6; unfold nat_of_P in |- *.
case (Pmult_nat p0 1); simpl in |- *; auto.
red in |- *; intros H'; discriminate.
Qed.
Hint Resolve NconvertO: zarith.

Theorem absolu_lt_nz : forall z : Z, z <> 0%Z -> 0 < Zabs_nat z.
intros z; case z; simpl in |- *; auto; try (intros H'; case H'; auto; fail);
intros p; generalize (NconvertO p); auto with arith.