题解 | #提取不重复的整数#

import java.util.*;

public class Main {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String str = scanner.next();
        StringBuilder result = new StringBuilder();
        while (str.length() > 0) {
            String substring = str.substring(str.length() - 1);
            str = str.replace(substring, "");
            result.append(substring);
        }
        System.out.println(result);
    }
}