(**)
intros U F F' F'' F''' n v w S0 S1 S2 S3 M i. assert(H:w i=preimg _(fun x:U=>v(
proj1_sig(simple_P0 _ _ _ _ S0 S1 S2 S3 x)))(fun r:R=>v i<=r<=v i)%R). apply
Extensionality_Ensembles. split. red. red. red. intros x H1. elim(simple_P0 _ n
v w S0 S1 S2 S3 x). simpl. intros j H2. elim H2. intros H3 H4. elim H4.
intros H5 H6. elim(H6 i). intuition. auto.
(**)
red. unfold preimg;unfold In. intros x H1. rewrite(S2 i (proj1_sig(simple_P0 _
n v w S0 S1 S2 S3 x))). 2:intuition. elim(simple_P0 _ n v w S0 S1 S2 S3 x).
simpl. intuition. rewrite H. apply M. apply borl_1. apply borl_0. apply
compact_P2. apply compact_P3. Qed.

(* Specifications: *)
Lemma simple_P4:
forall(U:Type)(A:Ensemble U),
simple_0 _ 2(fun i:nat=>INR i)(fun i:nat=>if eq_nat_dec i 0 then Complement _ A
else if eq_nat_dec i 1 then A else Empty_set _).