using System;

using System.Threading.Tasks;

class Program

{

   public static void Main(string[] args)

   {

      var a =  F();

      var b =  F();

      Console.WriteLine(a.Result + b.Result);

   }

   static async Task<int> F()

   {

      await Task.Delay(2000);

      return 5;

   }

}

​