using System;

using System.Threading.Tasks;

using System.Threading;

using System.Collections.Generic;

public class Program

{

    public async void Main()

    {       

        var T1 = await Sum(2,5);

        var T2 = await Sum(T1, 7);

        var T3 = await Sum(T2, 7);      

        Console.WriteLine(T3);

    }

    public async Task<int> Sum(int num1, int num2){

        return await Task.Factory.StartNew(() => {

            // for some reason if i use Sleep... I don't see any results at all...

            //Thread.Sleep(2000);

            return num1 + num2;

        });

    }

}