fact: Definition compute_pr1_dni_first (n : nat) (i: ⟦n⟧ ) : pr1 (dni firstelement i) = S (pr1 i).
imports: UniMath.Foundations.NaturalNumbers UniMath.MoreFoundations.Tactics UniMath.MoreFoundations.DecidablePropositions UniMath.MoreFoundations.NegativePropositions