#include <bits/stdc++.h>
#define ll long long
#define MOD 997
using namespace std;
ifstream fin("ordine.in");
ofstream fout("ordine.out");
string s;
int fv[130];

int main() {
    fin >> s;
    sort(s.begin(), s.end());
    bool stop;
    do {
        stop = true;
        for (int i = s.size() - 1; i > 0; --i)
            if (s[i] == s[i - 1]) {
                swap(s[i], s[i + 1]);
                stop = false;
            }
    } while(!stop);
    fout << s;
    return 0;
}