Require Import Omega.

Goal forall x, 0 <= x -> x <= 20 -> 
x <> 0  
  -> x <> 1 -> x <> 2 -> x <> 3 -> x <>4 -> x <> 5 -> x <> 6 -> x <> 7 -> x <> 8
-> x <> 9 -> x <> 10 
  -> x <> 11 -> x <> 12 -> x <> 13 -> x <> 14 -> x <> 15 -> x <> 16 -> x <> 17
-> x <> 18 -> x <> 19 -> x <> 20 -> False.
Proof.
  intros.
  Fail omega.
Abort.