using System;

using System.Linq;

using System.Diagnostics;

using System.Threading;

using System.Threading.Tasks;

using System.Collections.Concurrent;

public class Program

{

    public static void Main()

    {

        var cb = new ConcurrentBag<TimeSpan>();

        var sw = Stopwatch.StartNew();

​

        var timer = new System.Timers.Timer();

        timer.Interval = TimeSpan.FromSeconds(1.0).TotalMilliseconds;

        timer.Elapsed += (s, e) =>

        {

            cb.Add(sw.Elapsed);

            Thread.Sleep(TimeSpan.FromSeconds(0.5));

        };

        timer.Enabled = true;

​

        Thread.Sleep(TimeSpan.FromSeconds(9.0));

​

        timer.Enabled = false;

​

        cb.ToArray().OrderBy(x => x).Buffer(2).Where(x => x.Count == 2).Select(x => x[1].Subtract(x[0])).Dump();

    }

}