proposition: Lemma axiom_19 : forall (a : nadd), (mk_nadd (dest_nadd a)) = a.
proof: Proof. intros [f h]. simpl. apply eq_nadd. simpl. rewrite <- axiom_20. exact h. Qed.
imports: Coq.Logic.ClassicalEpsilon ClassicalFacts PropExtensionalityFacts Lia PeanoNat ProofIrrelevance ExtensionalityFacts List Coq.Strings.Ascii