using System;

public class Test
{
    public static bool IsPalindrome(string value)
    {
        if ( string.IsNullOrEmpty(value) )
            return true;

        return isPalindrome(value, 0, value.Length - 1);
    }

    private static bool isPalindrome(string value, int startChar, int endChar)
    {
        if ( value[startChar] != value[endChar] )
            return false;

        if ( startChar >= endChar )
            return true;

        return isPalindrome(value, startChar + 1, endChar - 1);
    }
    
	public static void Main()
	{
        Console.WriteLine(IsPalindrome(""));
        Console.WriteLine(IsPalindrome("1"));
        Console.WriteLine(IsPalindrome("11"));
        Console.WriteLine(IsPalindrome("121"));
        Console.WriteLine(IsPalindrome("123"));
	}
}