public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        while(sc.hasNext()){
            String str = sc.next();
            char[] ch = str.toCharArray();
            for(int i = 0; i < ch.length - 1; i++){
                char temp;
                for(int j = i; j < ch.length; j++){
                    if(ch[i] == ch[j]){
                        continue;
                    }
                    if(ch[i] > ch[j]){
                        temp = ch[i];
                        ch[i] = ch[j];
                        ch[j] = temp;
                    }
                }
            }
            System.out.println(String.valueOf(ch));
        }
    }
}