using System;

public class Program

{

    public static void Main()

    {

        string s1 = string.Format("{0}{1}", "abc", "cba");

string s2 = "abc" + "cba";

string s3 = "abccba";

Console.WriteLine(s1 == s2);

Console.WriteLine((object)s1==(object)s2);

Console.WriteLine(s2==s3);

Console.WriteLine((object)s2==(object)s3);

    }

}