326.
What will the following produce:
static void Main(string[] args)
{
    Display(1);
    Display("1");
    Display(null);
}
public static void Display(int? num)
{
    Console.WriteLine(num);
}
public static void Display(string num)
{
    Console.WriteLine(num);
}

The call is ambiguous between the following methods or properties: 
Program.Display(int?) and Program.Display(string) because NULL can be accepted by both functions. (This has been verified)