Section B.
Variable R1 R2 S1 S2 H S : Z.
Hypothesis I : (R1 < 0)%Z -> R2 = (R1 + (2 * S1 - 1))%Z.
Hypothesis J : (R1 < 0)%Z -> S2 = (S1 - 1)%Z.
Hypothesis K : (R1 >= 0)%Z -> R2 = R1.
Hypothesis L : (R1 >= 0)%Z -> S2 = S1.
Hypothesis M : (H <= 2 * S)%Z.
Hypothesis N : (S < H)%Z.
lia.
Qed.
End B.

(* From Nicolas Oury (BZ#180): handling -> on Set (fixed Oct 2002) *)
Lemma lem6 :
forall (A : Set) (i : Z), (i <= 0)%Z -> ((i <= 0)%Z -> A) -> (i <= 0)%Z.