Intersection by Merge

public static Cons intersectionm (Cons x, Cons y) {
  return mergeint(llmergesort(x), llmergesort(y));}

public static Cons mergeint (Cons x, Cons y) {
  if ( x == null || y == null ) return null;
   else if ( first(x).equals(first(y)) )
           return cons(first(x),
                       mergeint(rest(x),rest(y)));
  else if ( ((Comparable) first(x))
                         .compareTo(first(y)) < 0)
      return mergeint(rest(x), y);
  else return mergeint(x, rest(y));}

(defun intersection (x y)
  (mergeint (llmergesort x) (llmergesort y)) )
(defun mergeint (x y)
  (if (or (null x) (null y))
      nil
      (if (= (first x) (first y))
          (cons (first x)
                (mergeint (rest x) (rest y)))
          (if (< (first x) (first y))
              (mergeint (rest x) y)
              (mergeint x (rest y)) ) ) ) )

What is O()? Stack depth? Conses?