proposition: Lemma addNz : left_inverse (0:int) oppz addz.
proof: Proof. by do 3?elim. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)