using System;

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Enter a word:");

        string s = Console.ReadLine();

        string output = "";

​

        foreach (char c in s)

        {

            if (char.IsLower(c) && !output.Contains(c))

            {

                output += c;

            }

        }

​

        Console.WriteLine(output);

    }

}