#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int main(){
	vector<char> data;
	char x;
	while(cin >> x) data.push_back(x);
	sort(data.begin(),data.end(),greater<int>());
	for(auto x:data) cout << x;
	cout << endl;
	return 0;
}