using System;

using System.Threading.Tasks;

using System.Diagnostics;

public class Program

{

    public static async Task Main()

    {

        Stopwatch stopwatch = Stopwatch.StartNew();

​

        Task t1 = Task.Delay(1000);

        Task t2 = Task.Delay(1000);

        Task t3 = Task.Delay(1000);

        await t1; await t2; await t3;

        Console.WriteLine($"Duration: {stopwatch.ElapsedMilliseconds:#,0} msec");

​

        await Task.Delay(1000); 

        await Task.Delay(1000); 

        await Task.Delay(1000);

​

        Console.WriteLine($"Duration: {stopwatch.ElapsedMilliseconds:#,0} msec");

    }

}

​