using System;

using System.Collections.Generic;

using System.Diagnostics;

using System.Linq;

using System.Threading.Tasks;

public class Program

{

    public static void Main()

    {

        var x = AsyncMain().Result;

    }

    public static async Task<int> AsyncMain()

    {

        Console.WriteLine("Hello World");

        var sw = Stopwatch.StartNew();

        var tasks = Enumerable.Range(1, 100).Select(async (x) => { await Task.Delay(500); Console.WriteLine(x); }).ToList();

        await Task.WhenAll(tasks);

        sw.Stop();

        Console.WriteLine("Execution is {0}", sw.ElapsedMilliseconds);

        return 0;

    }

}