Definition hz_normal_form (i:ℤ) := coprod (∑ n, natnattohz n 0 = i) (∑ n, natnattohz 0 (S n) = i).
Require Import UniMath.MoreFoundations.PartA. Require Import UniMath.Algebra.Monoids. Require Import UniMath.Algebra.Groups.