class SortedIntegerSet {
  private SetNode first, last;
  private int numItems;

  public SortedIntegerSet() {
    last = new SetNode(0, null);  // Problem, hier wird schon ein Eintrag erstellt
    first = last;

    numItems = 0;
  }

  public int size() {
    return numItems;
  }

  public boolean isEmpty() {
    return (first == last);
  }

  public int insert(int data) {
    SetNode cur = first;
    for (int i = 0; i < numItems; i++) {
      if (cur.next.data < data)
        cur = cur.next;
      else {
        cur.next = new SetNode(data, cur.next);
        numItems++;
        return 0;
      }
    }
    last.next = new SetNode(data, null);
    last = last.next;
    numItems++;
    return 0;
  }

  public String toString() {
    SetNode cur = first;
    String ret = "";
    for (int i = 0; i < numItems; i++) {
      ret += cur.data + " ";
      cur = cur.next;
    }
    return ret;
  }
}

class SetNode {
  int data;
  SetNode next;

  public SetNode(int data, SetNode next) {
    this.data = data;
    this.next = next;
  }
}



class Main {
  public static void main(String[] args) {
    SortedIntegerSet sis = new SortedIntegerSet();
    sis.insert(9);
    sis.insert(10);
    sis.insert(4);
    sis.insert(7);
    System.out.println(sis);

  }
}