Lemma hzrminusplus (n m : hz) : n - m + m = n. Proof. unfold hzplus, hzminus. rewrite ringassoc1. rewrite hzlminus. apply hzplusr0. Defined.
Require Import UniMath.MoreFoundations.PartA. Require Import UniMath.Algebra.Monoids. Require Import UniMath.Algebra.Groups.