using System;

public class DuplicateLetters

{

    public static void Main()

    {

        String str;

        Console.WriteLine("enter string");

        str = Console.ReadLine();

        Console.WriteLine("String: "+str);

        int i=0;

        while(str.Length>0 && i<str.Length)

        {

            int count=0;

            for(int j=1;j<str.Length;j++)

            {

                if(str[i]==str[j])

                    count++;

            }

            if(count<2)

                Console.WriteLine(str[i]);

            i++;

        }

    }

}