using System;
using System.Threading;

namespace Multithread_Computation
{
    class Program
    {
        private static Semaphore _pool;
        static int a = 1,
            b = 3,
            c = 6,
            d = 2,
            e = 4,
            f = 8;

        static int res1, res2, res3, res4;

        static int[] SharedTable = new int[5];
        static int i = 0;

        static void Main(string[] args)
        {

            _pool = new Semaphore(1, 2);

            Thread t1 = new Thread(new ThreadStart(Thread1));
            Thread t2 = new Thread(new ThreadStart(Thread2));
            Thread t3 = new Thread(new ThreadStart(Thread3));
            Thread t4 = new Thread(() => Thread4(t3));




            t1.Start();
            t2.Start();
            t3.Start();
            t1.Join();
            t2.Join();
            t4.Start();

            Thread.Sleep(1000);

            _pool.Release();

        }


        static void Thread1()
        {
            _pool.WaitOne();

            SharedTable[i] = a + b;

            res1 = i;

            i++;

            _pool.Release();
        }
        static void Thread2()
        {
            _pool.WaitOne();

            SharedTable[i] = c + d;

            res2 = i;

            i++;

            _pool.Release();
        }
        static void Thread3()
        {
            _pool.WaitOne();

            SharedTable[i] = e + f;

            res3 = i;

            i++;

            _pool.Release();
        }
        static void Thread4(Thread t3)
        {
            _pool.WaitOne();

            SharedTable[i] = SharedTable[res1] * SharedTable[res2];

            res4 = i;
            i++;

            t3.Join();

            SharedTable[i] = SharedTable[res4] * SharedTable[res3];

            Console.WriteLine("(" + a + " + " + b + ")(" + c + " + " + d + ")(" + e + " + " + f + ")" + " = " + SharedTable[i]);


            _pool.Release();
        }

    }
}