fun append (x, y) {
    case x of
      `nil         -> return y
    | `cons (h, t) -> return `cons (h, append (t, y))
    esac
}

fun printList (x) {
    case x of
      `nil         -> skip
    | `cons (h, t) -> write (h); printList (t)
    esac
}

n := read ();

x := `cons (1, `cons (2, `nil));
y := `cons (3, `cons (4, `nil));

printList (x);
printList (y);
printList (append (x, y));
printList (append (y, x))