using System;

struct MyTypeA
{
	short b;

	public MyTypeA (short b)
	{
		this.b = b;
	}

	public static MyTypeA operator + (MyTypeA a, MyTypeA b)
	{
		throw new NotSupportedException ();
	}
	
	public static bool operator == (MyTypeA a, MyTypeA b)
	{
		return true;
	}
	
	public static bool operator != (MyTypeA a, MyTypeA b)
	{
		throw new NotSupportedException ();
	}
	
	public static bool operator > (MyTypeA a, MyTypeA b)
	{
		throw new NotSupportedException ();
	}

	public static bool operator < (MyTypeA a, MyTypeA b)
	{
		throw new NotSupportedException ();
	}
}

struct MyTypeB
{
	short b;

	public MyTypeB (short b)
	{
		this.b = b;
	}

	public static MyTypeB operator + (MyTypeB a, MyTypeB b)
	{
		return a;
	}
	
	public static bool operator == (MyTypeB a, MyTypeB b)
	{
		return true;
	}
	
	public static bool operator != (MyTypeB a, MyTypeB b)
	{
		return false;
	}
	
	public static bool operator > (MyTypeB a, MyTypeB b)
	{
		return false;
	}

	public static bool operator < (MyTypeB a, MyTypeB b)
	{
		return true;
	}
	
	public static MyTypeB operator & (MyTypeB a, MyTypeB b)
	{
		return a;
	}
}

class C
{
	public static int Main ()
	{
		MyTypeA? mt = null;
		mt = null + mt;
		
		MyTypeA? mt2 = null;
		mt2 = mt2 + null;
		bool b = mt2 > null;
		bool x = mt2 == null;
		
		MyTypeB? bt = null;
		bt = bt + bt;
		if (bt != null)
			return 2;
			
		MyTypeB? b2 = null;
		bool bb = b2 == b2;
		if (!bb)
			return 3;
		
		MyTypeB? b3 = null;
		b3 = b3 & b3;
		return 0;
	}
}