import java.util.*;
import java.lang.*;
import java.io.*;
 
public class Main {
    public static void main(String[] args) {
     BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
     String line ;
        try{
        char fr[] = new char[26] ;
        while((line = reader.readLine()) != null){
            for(int i = 0 ; i < line.length() ; i++){
 
                for(int j = i + 1 ; j < line.length() ; j++ ){
                    if( line.charAt(i) == line.charAt(j) ){
                        fr[i] = line.charAt(i) ;
 
                    }else{
                    	fr[i] = fr[i + 1] ;
                    }
                }
                System.out.print(fr[i]);
            }
 
        }
 
    }catch(Exception e){
        e.printStackTrace();
      }
    }
}

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Ym9vcw==

boos