Lemma isdecrelhzeqminusplus' (i j : hz) : isdecrelhzeq (i - j + j) i = ii1 (hzrminusplus i j). Proof. induction (isdecrelhzeq (i - j + j) i) as [T | F]. - apply maponpaths. apply isasethz. - apply fromempty. apply F. apply (hzrminusplus i j). Qed.
Require Import UniMath.MoreFoundations.PartA. Require Import UniMath.Algebra.Monoids. Require Import UniMath.Algebra.Groups.