using System;
using System.Threading;

public class Test
{
	static void Main()
	{
	    new Train(true);
	    new Train(true);
	    Thread.Sleep(100);
	    new Train(false);
	    new Train(true);
	    new Train(false);
	    Console.Read();
	}
}

class Railway
{
    public static Semaphore lock1 = new Semaphore(1, 1);
}
 
class Train
{
    static Semaphore w_turnstile = new Semaphore(1, 1);
    static Semaphore w_mutex = new Semaphore(1, 1);
    static int w_counter = 0;
    static Semaphore e_turnstile = new Semaphore(1, 1);
    static Semaphore e_mutex = new Semaphore(1, 1);
    static int e_counter = 0;
 
    bool West;
    public Thread Thrd;
    
    public Train(bool west)
    {
        West = west;
        Thrd = new Thread(this.Run);
        Thrd.Name = west ? "запад" : "восток";
        Thrd.Start();
    }
    
    private Semaphore turnstile { get { return West ? w_turnstile : e_turnstile; } }
    private Semaphore turnstile2 { get { return West ? e_turnstile : w_turnstile; } }
    private Semaphore mutex { get { return West ? w_mutex : e_mutex; } }
    private int counter { get { return West ? w_counter : e_counter; } }
    
    private void Inc()
    {
        if(West) w_counter++; else e_counter++;
    }
    
    private void Dec()
    {
        if(West) w_counter--; else e_counter--;
    }
    
    
    void Run()
    {
        Console.WriteLine("- Подошёл поезд на {0}", Thrd.Name);
    
        turnstile.WaitOne();
        turnstile.Release();
     
        mutex.WaitOne();
        Inc();
        if(counter == 1)
        {
            turnstile2.WaitOne();
            Railway.lock1.WaitOne();
            Console.WriteLine("! Стрелка на {0}", Thrd.Name);
            turnstile2.Release();
        }
        mutex.Release();
 
        //движение поезда
        Console.WriteLine("( Едет поезд на {0} ({1})", Thrd.Name, counter);
        Thread.Sleep(1000);
 
        mutex.WaitOne();
        Dec();
        if(counter == 0)
        {
            Railway.lock1.Release();
        }
        mutex.Release();    
        Console.WriteLine(") Проехал поезд на {0}  ({1})", Thrd.Name, counter);
    }
}