proposition: Lemma dni_first {n : nat} (i: ⟦n⟧ ) : pr1 (dni firstelement i) = S i.
proof: Proof. intros. apply idpath. Defined.
imports: UniMath.Foundations.NaturalNumbers UniMath.MoreFoundations.Tactics UniMath.MoreFoundations.DecidablePropositions UniMath.MoreFoundations.NegativePropositions