proposition: Lemma actpermM : {in D &, {morph actperm : a b / a * b}}.
proof: Proof. by move=> a b Da Db; apply/permP=> x; rewrite permM !permE actMin. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat div seq) mathcomp(fintype bigop finset fingroup morphism perm) mathcomp(automorphism quotient)