proposition: Lemma hzrminusplus (n m : hz) : n - m + m = n.
proof: Proof. unfold hzplus, hzminus. rewrite ringassoc1. rewrite hzlminus. apply hzplusr0. Defined.
imports: UniMath.Foundations.NaturalNumbers UniMath.MoreFoundations.PartA UniMath.MoreFoundations.NegativePropositions UniMath.Algebra.Monoids UniMath.Algebra.Groups UniMath.Algebra.RigsAndRings UniMath.NumberSystems.NaturalNumbersAlgebra