#include<bits/stdc++.h>
using namespace std;

typedef struct ac{
	char c;
	int num;
}ac;

bool cmp(ac a, ac b){
	if(a.num == b.num) return a.c < b.c;
	return a.num > b.num;
}

int main(){
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	string s;
	while(cin >> s){
		map<char, int>mp;
		int ls = s.length();
		ac a[ls];
		for(int i = 0; i < ls; i++){
			mp[s[i]]++;
		}
		int cnt = 0;
		for(map<char, int>::iterator it = mp.begin(); it != mp.end(); it++){
			char c = it->first;
			int m = it->second;
			a[cnt].c = c;
			a[cnt].num = m;
			cnt++;
		}
		sort(a, a + cnt, cmp);
		for(int i = 0; i < cnt; i++){
			for(int j = 0; j < a[i].num; j++) cout << a[i].c;
		}
		cout << endl;
	}
	return 0;
}