proposition: Lemma stn_right_first (n i : nat) : stn_right i (S n) firstelement = make_stn (i + S n) i (natltplusS n i).
proof: Proof. intros. apply subtypePath_prop. simpl. apply natplusr0. Defined.
imports: UniMath.Foundations.NaturalNumbers UniMath.MoreFoundations.Tactics UniMath.MoreFoundations.DecidablePropositions UniMath.MoreFoundations.NegativePropositions