#include <bits/stdc++.h>
using namespace std;
int main() {
    string s;
    while (getline(cin,s)) {
        vector<int> val;
        for (int i=0; i<s.length(); i++) {
            val.push_back(s[i]-'a');
        }
        sort(val.begin(), val.end());
        for (int i=0; i<val.size(); i++) {
            char c=val[i]+'a';
            cout<<c;
        }

    }
}