proposition: Lemma eq_mulVg1 x y : (x == y) = (x^-1 * y == 1 :> T).
proof: Proof. by rewrite -eq_invg_mul invgK. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)