public class IntInterval: IntSequence{

  private int from, to;

  public IntInterval(int from, int to){
    this.from = from;
    this.to = to;
  }

  public override int? Min{
    get {return Math.Min(from,to);}
  }

  public override int? Max{
    get {return Math.Max(from,to);}
  }
    
  public override IEnumerator GetEnumerator (){
    if (from < to)
     for(int i = from; i <= to; i++)
       yield return i;
    else
     for(int i = from; i >= to; i--)
       yield return i;
  }

}