import java.util.HashSet;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String str = scanner.nextLine();
        scanner.close();
        HashSet<Character> hs = new HashSet<>();
        for (int i=0;i<str.length();i++)
        {
            hs.add(str.charAt(i));
        }
        for (char c:hs) {
            System.out.print(c);
        }
    }
}