Thread Synchronization Issue in C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Threading;
namespace ThreadSynchronizationIssue
{
    class Program
    {
        static int count = 0;
        static void Main(string[] args)
        {
            Thread thread1 = new Thread(Increment);
            Thread thread2 = new Thread(Increment);
            thread1.Start();
            Thread.Sleep(500);
            thread2.Start();
        }
        static void Increment()
        {
            while (true)
            {
                count++;
                Console.WriteLine("theadID {1} - This is SynchronizationIssue: {0}", count, Thread.CurrentThread.ManagedThreadId);
                Thread.Sleep(1000);
            }
        }
    }
}