Lemma isdecrelhzeqminusplus (i j : hz) : isdecrelhzeq i (i - j + j) = ii1 (hzrminusplus' i j). Proof. induction (isdecrelhzeq i (i - j + j)) 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.