intros.apply absurd (O \leq n1).apply le_O_n.assumption.
simplify.intros.apply le_S_S.apply le_O_n.
simplify.intros.apply le_S_S.apply H.intros.apply H1.apply le_S_S.
assumption.
qed.
intros.apply absurd (O \leq n1).apply le_O_n.assumption.
simplify.intros.apply le_S_S.apply le_O_n.
simplify.intros.apply le_S_S.apply H.intros.apply H1.apply le_S_S.
assumption.
qed.