fun f (x) {
  case x of
    `nil                                  -> write (0)
  | `cons (_, `nil)                       -> write (1)
  | `cons (_, `cons (_, `nil))            -> write (2)
  | `cons (_, `cons (_, `cons (_, `nil))) -> write (3)
  | _                                     -> write (4)
  esac
}

x := read ();
y := `nil;

for i := 0, i < 10, i := i + 1 do
  f (y);
  y := `cons (i, y)
od