proposition: Lemma mem_conjgV A x y : (y \in A :^ x^-1) = (y ^ x \in A).
proof: Proof. by rewrite mem_conjg invgK. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)