/**
*思路:先将输入的整数存入字符数组中,再加入到list集合,再加到list集合的过程中
*判断是否有重复数字,有则不存!(实现语句: !list.contains() ),没有则继续存!
*最后,创建StringBuilder拼接字符,输出即可!
*/
import java.util.*;
public class Main{
 public static void main(String[] args){
        Scanner scan = new Scanner(System.in);
        String number = scan.nextLine();
        int len = number.length();
        char[] cr = number.toCharArray(); //存入字符数组!
        StringBuilder stb = new StringBuilder();
        List<Character> list = new ArrayList<>(); //加入到list容器中!
        for (int i = len-1;i>=0;i--){    //从右向左读取
            if(!list.contains(cr[i])){  //判断去重语句!
                list.add(cr[i]);  
            }
        }
        for (char c:list){  //for增强循环遍历list的数据
            stb.append(c);  
        }
        System.out.println(stb.toString());
    }
}