public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        if(sc.hasNext()){
            String str = sc.nextLine();
            char[] chars=str.toCharArray();
            char temp;
            for(int i=0;i<chars.length;i++){
                for(int j=i+1;j<chars.length;j++){
                    if(chars[i]>chars[j]){
                        temp=chars[j];
                        chars[j]=chars[i];
                        chars[i]=temp;
                    }
                }
            }
            System.out.print(chars);
        }
    }
}