proposition: Lemma subgM : {in G &, {morph subg : x y / x * y}}.
proof: Proof. by move=> x y Gx Gy; apply: val_inj; rewrite /= !subgK ?groupM. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)