using System;
 
class Singleton {
        private static Singleton _instance;
        private int _counter;
        private Singleton() {
            _instance = null;
            this._counter = 0;
        }
 
        public static Singleton Instance{
            get {
                if (_instance == null) _instance = new Singleton();
                return _instance;
            }
        }
 
        public void Increment() {
            this._counter++;
            Console.WriteLine(this._counter);
        }
    }
 
 
public class Test
{
	public static void Main()
	{
		var first = Singleton.Instance;
		first.Increment();
 
		var second = Singleton.Instance;
		second.Increment();
	}
}

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