proposition: Lemma lcoset_sym x y : (x \in y *: G) = (y \in x *: G).
proof: Proof. by rewrite !mem_lcoset -groupV invMg invgK. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)