using System;

public class Program

{

    public static void Main()

    {

        UnitTest();

    }

    public static void UnitTest()

    {

        var text1 = "";

        var text2 = "aa";

        var text3 = "abcdea";

        var text4 = "qwerty";

        if (IsUnique(text1))

            Console.WriteLine("Success");

        else

            Console.WriteLine("Failed");

        if (!IsUnique(text2))

            Console.WriteLine("Success");

        else

            Console.WriteLine("Failed");

        if (!IsUnique(text3))

            Console.WriteLine("Success");

        else

            Console.WriteLine("Failed");

        if (IsUnique(text4))

            Console.WriteLine("Success");

        else

            Console.WriteLine("Failed");    }

    public static bool IsUnique(string text)

    {

        var letters = text.ToCharArray();

        Array.Sort<char>(letters);

        for(int i = 1; i<letters.Length; i++)

        {

            if(letters[i] == letters[i-1])

                return false;

        }

        return true;

    }

}