inteface Iterator<A> {
  public boolean hasNext();
  public A next();
}

class Interval implements Iterator<Integer> {
  private int i;
  private int n;
  public Interval(int l, int u) { i = l; n = u; }
  public boolean hasNext() { return (i <= n); }
  public Integer next() { return new Integer(i++); }
}