using System;

class Program
{
    static void Main()
    {
        string a = "hello";
        string b = "he" + "llo";

        Console.WriteLine(object.ReferenceEquals(a, b));
    }
}

using System;

class Program
{
    static void Main()
    {
        int[] numbers = { 1, 2, 3 };

        foreach (var n in numbers)
        {
            int copy = n;

            copy++;
        }

        Console.WriteLine(string.Join(" ", numbers));
    }
}

using System;

class Program
{
    static void Main()
    {
        int? x = null;

        Console.WriteLine(x is int);
    }
}

using System;

class Program
{
    static void Print(object x)
    {
        Console.Write("object");
    }

    static void Print(string x)
    {
        Console.Write("string");
    }

    static void Main()
    {
        Print(null);
    }
}

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        var dict = new Dictionary<int, string>();

        dict[1] = "A";
        dict[1] = "B";

        Console.WriteLine(dict.Count);
    }
}