using System;
using System.IO;
using System.Xml;
using System.Xml.XPath;
using System.Collections;


public class Cap4_Ex30_Test {

  public static void Main(string[] args) {
    XmlTextReader r = new XmlTextReader("organizer.xml");
    long sum = 0;
    DateTime s , e;
    s = new DateTime(2004,1,1,1,1,1);
    while (r.Read()) {
      if (r.IsStartElement("start")) {
        r.Read();  //  read the start date
        s = DateTime.Parse(r.Value);
      } 
      else if (r.IsStartElement("end")) {
        r.Read();  //  read the end date
        e = DateTime.Parse(r.Value);
        TimeSpan ts = e.Subtract(s);
        sum += (long)ts.TotalMilliseconds;
      }
    }
    Console.WriteLine("Sum of task durations in ms:{0}", sum);
    r.Close();
  }
}