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

class Program { 
  static volatile int s_x; 
  static volatile int s_xa; 
  static volatile int s_y; 
  static volatile int s_ya; 

  static void Main(string[] args) { 
    while (true) { 
      s_x = 0; s_xa = 0; s_y = 0; s_ya = 0;
      Task A = Task.Factory.StartNew(() => { 
                    s_x = 1; // W
                    s_ya = s_y; // W, R
               }); 
      Task B = Task.Factory.StartNew(() => { 
                    s_y = 1; // W
                    s_xa = s_x; // W, R
               }); 
      Task.WaitAll(A, B); 
      if (!(s_xa == 1 || s_ya == 1)) Console.WriteLine("* {0}, {1}", s_xa, s_ya); 
    } 
  } 
}