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

int a, b, c;
map<string, int> s; 

int main(void) {
    ios::sync_with_stdio(0); cin.tie(0); 
    string t; cin >> t; 
    for (int i = 0; i < t.size(); ++i) {
        char it = t[i]; 
        string to = ""; 
        to += t[i]; 
        ++s[to]; 
    }
    while (s.size() > 1) {
        auto [_S, Sc] = *s.begin(); auto S = _S; 
        auto [_T, Tc] = *--s.end(); auto T = _T; 
        s.erase(s.begin()), s.erase(prev(s.end())); 
        int x = (Tc - 1) / Sc, y = (x + 1) * Sc - Tc; 
        while (x--) S += T; 
        if (y) s[S] = y; 
        if (Sc - y) s[S + T] = Sc - y; 
    }
    auto [S, Sc] = *s.begin();
    while (Sc--) cout << S; cout << "\n"; 
    return 0; 
}