using System;

using System.Threading;

using System.Threading.Tasks;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        Task<int> t = null;

        for(int i=0; i<20; i++){

            if(t == null || t.IsCompleted){

                t = Task.Run(() => LaunchTask());

            }

            Task.Run(() => Require(t));

            Thread.Sleep(30);

        }

    }

    public static async void Require(Task<int> t){

        int x = await t;

        Console.WriteLine(x);

        Console.WriteLine(DateTime.Now.Ticks/10000); // 1 tick = 0.0000001 second

    }

    public static int LaunchTask(){

        Console.WriteLine("Task launched");

        Thread.Sleep(100);

        return 42;

    }

}