{
        T[] buf = new T[BUFSIZE];
        int start = 0;
        int end = 0;
        SemaphoreSlim canReadCountSemaphoreSlim = new SemaphoreSlim(0);
        SemaphoreSlim canWriteCountSemaphoreSlim = new SemaphoreSlim(BUFSIZE);
        
        public T Dequeue()
        {            
            canReadCountSemaphoreSlim.Wait(); 
            
            int i = Interlocked.Decrement(ref end);
            T val = Volatile.Read(ref buf[i]);                        
            
            canWriteCountSemaphoreSlim.Release();            
            return val;            
        }        
        public void Enqueue(T val)        
        {                        
            canWriteCountSemaphoreSlim.Wait();
            
            int i = Interlocked.Decrement(ref start);
            Volatile.Write(ref buf[i], val);
                        
            canReadCountSemaphoreSlim.Release();            
        }
}

using System.Threading;
namespace Program
{
    public class BlockingRingQueue<T> where T: class
    {
        const int BUFSIZE_LOG2 = 10;
        const int BUFSIZE = 1 << BUFSIZE_LOG2;
        
        T[] buf = new T[BUFSIZE];
        int start = 0;
        int end = 0;
        SemaphoreSlim canReadCountSemaphoreSlim = new SemaphoreSlim(0);
        SemaphoreSlim canWriteCountSemaphoreSlim = new SemaphoreSlim(BUFSIZE);
        
        public T Dequeue()
        {            
            canReadCountSemaphoreSlim.Wait();
            
            int i = Interlocked.Decrement(ref end);
            i = PositiveMod(i, BUFSIZE);
            T val = Volatile.Read(ref buf[i]);
                        
            canWriteCountSemaphoreSlim.Release();            
            return val;            
        }
        
        public void Enqueue(T val)        
        {                        
            canWriteCountSemaphoreSlim.Wait();
            
            int i = Interlocked.Decrement(ref start);
            i = PositiveMod(i, BUFSIZE);
            Volatile.Write(ref buf[i], val);
                        
            canReadCountSemaphoreSlim.Release();            
        }
        
        static int PositiveMod(int a, int b) => ((a % b) + b) % b;
    } 
}