proposition: Fact fmod_addNr : left_inverse (sub2f 1) fmod_opp fmod_add.
proof: Proof. by move=> u; apply: val_inj; apply: mulVg. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq path) mathcomp(div choice fintype bigop ssralg finset fingroup) mathcomp(morphism perm finalg action gproduct commutator) mathcomp(cyclic)