题解 | #提取不重复的整数#

import java.util.Scanner;

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        String s = "";
        while (s.length() == 0) {
            s = in.next();
        }
        char[] chars = s.toCharArray();
        Set<Character> set = new LinkedHashSet<>();
        for (int i = chars.length; i > 0; i --) {
            set.add(chars[i - 1]);
        }
        String output = "";
        for (Character c : set) {
            output = output + c;
        }
        System.out.println(output);
    }
}