proposition: Lemma permS0 : all_equal_to (1 : 'S_0).
proof: Proof. by move=> g; apply/permP; case. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(choice fintype tuple finfun bigop finset binomial) mathcomp(fingroup morphism)