Lemma hzeqpii {i : hz} : i - 1 != i. Proof. apply (negf (λ e, hzpluslcan _ _ _ (e @ ! hzplusr0 i))); clear i. confirm_not_equal isdecrelhzeq. Qed.
Require Import UniMath.MoreFoundations.PartA. Require Import UniMath.Algebra.Monoids. Require Import UniMath.Algebra.Groups.