induction 1; intuition.
inversion H; clear H; subst; eauto with  dat.
inversion H1; clear H1; subst.
econstructor.
econstructor; eauto.
Qed.

Lemma dat_correct_dat_better : forall (A : Set)(c : Comp A) ls n1 t1,
dat_correct_h c ls n1 t1 ->
forall n2 t2,
dat_correct_h c ls n2 t2 ->
n1 >= n2 ->
dat_better t1 t2.