proposition: Lemma actmM a : {in R &, {morph actm to a : x y / x * y}}.
proof: Proof. by rewrite /actm; case: ifP => //; apply: gactM. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat div seq) mathcomp(fintype bigop finset fingroup morphism perm) mathcomp(automorphism quotient)