#include <iostream>
#include <vector>
#include <cstdio>
#include <sstream>
#include <map>
#include <string>
#include <algorithm>
#include <queue>
#include <cmath>
#include <set>
using namespace std;

int main(){
	string s;
	cin >> s;
	sort(s.rbegin(), s.rend());
	cout << s << endl;
	return 0;
}