Ltac show_stopped :=
  let m' := fresh "m'" in
  let e' := fresh "e'" in
  let H := fresh "H" in
  right; intros [m' [e' H]]; inv H.

Lemma stopped_Update: forall m e1 e2 e3, stopped m (Update e1 e2 e3) -> stopped m e1 \/ (isValue e1 /\ stopped m e2).