Goal:
    A : Type  n : nat  hd : A  tl : list A  H : S n < #|hd :: tl|
  ============================
   (S n ≤ #|tl|)


DEBUG:Going to execute:
match goal with
           | H:?x ≠ ?x |- _ => elim H; Ltac.reflexivity
           | _ => discriminate
           end