Goal:
  
  A : Type
  B : Type
  P : nat → A → B → Type
  n : nat
  x : A
  c : B
  n0 : nat
  ============================
   (None = Some x → None = Some c → P (n0 + n) x c)


DEBUG:Going to execute:
done
DEBUG LTAC Evaluated term: nth_error_nil
DEBUG LTAC Evaluated term: nth_error_nil
DEBUG LTAC Evaluated term: nth_error_nil
DEBUG LTAC Evaluated term: nth_error_nil