Lemma plusmn0m0 m n : m + n = 0 -> m = 0. Proof. intros i. assert (a := natlehnplusnm m n). rewrite i in a. apply natleh0tois0. assumption. Defined.
Require Import UniMath.Foundations.All. Require Import UniMath.MoreFoundations.Tactics. Require Import UniMath.MoreFoundations.PartA.