using System;

using System.Threading;

using System.Threading.Tasks;

using System.Collections.Generic;

public class Program {

    public async Task<bool> Execute(Action action) {

        await Task.Run(() => action());

        return true;

    }

    public static void Main() {

        Console.WriteLine("Hello World");

        var program = new Program();

        var tasks = new List<Task<bool>>() {

            program.Execute(() => { Thread.Sleep(500); Console.WriteLine("task1"); }),

            program.Execute(() => { Thread.Sleep(100); Console.WriteLine("task2"); }),

            program.Execute(() => { Thread.Sleep(250); Console.WriteLine("task3"); }),

        };

        var taskAll = program.Execute(() => {

            Console.WriteLine("run");

            Task.WaitAll(tasks.ToArray());

            Console.WriteLine("All Done!");

        });

        taskAll.Wait();

    }

}