using System;

using System.Collections.Generic;

using System.Threading.Tasks;

public class Program

{

    public static void Main()

    {

        new Program().execute();

    }

    async void execute() {

        Console.WriteLine("Hello, World!");

        Console.WriteLine("Two await false");

        await A().ConfigureAwait(false);

        await B().ConfigureAwait(false);

        Console.WriteLine("Two await true");

        await A().ConfigureAwait(true);

        await B().ConfigureAwait(true);

        Console.WriteLine("No await");

        Task a = A();

        Task b = B();

        await Task.WhenAll(a, b).ConfigureAwait(false);

        Console.WriteLine("Bye, World!");

        async Task A()

        {

            for (int i = 0; i < 10; i++)

            {

                Console.WriteLine($"A: {i}");

                await Task.Delay(100);

            }

        }

        async Task B()

        {

            for (int i = 0; i < 15; i++)

            {

                Console.WriteLine($"B: {i}");

                await Task.Delay(80);

            }

        }

    }

}