import java.util.*;
import java.util.stream.Collectors;
public class Main {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
while(scanner.hasNext()) {
String l = scanner.nextLine();
List<String> list = new ArrayList<>();
for(int i = 0; i < l.length(); i++) {
if(i == l.length()-1) {
list.add(l.substring(i)) ;
break;
}
list.add(l.substring(i, i+1));
}
Collections.reverse(list);
// Set<String> set = list.stream().collect(Collectors.toSet());
// set.forEach(e -> System.out.print(e));
List<String> value = new ArrayList<>();
for (String s : list) {
if(!value.contains(s)) {
value.add(s);
}
}
value.forEach(e -> System.out.print(e));
}
}
}