using System;
using System.Threading;
using System.Threading.Tasks;

class Program {
  public static int Add(int a, int b) {
     Console.WriteLine("Child thread starts");
     int result = a + b;
     
     Console.WriteLine("Child thread goes to sleep");
     Thread.Sleep(5000); // the thread is paused for 5000 milliseconds
     
     Console.WriteLine("Child thread resumes and finishes");
     return result;
  }
  
  public static async Task<int> AddAsync(int a, int b)
  {
    int result = await Task.Run(() => Add(a, b));
	Console.WriteLine("Result computed = {0}", result);
	return result;
  }
  
  public static void Main(string[] args) {
     int x = 30;
     int y = 12;
     
     Console.WriteLine("Main thread starts");
     Task<int> task = AddAsync(x, y);

     Console.WriteLine("Main thread waiting");
     int sum = task.Result;
     Console.WriteLine("Main thread finishes, sum = {0}", sum);
  }
}