#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N=1e6+5;
string s;
map<string,int>q;
signed main(){
    cin>>s;
    for(int i=0;i<s.size();i++){
        string t;
        t+=s[i];
        q[t]++;
    }
    while(q.size()>1){
        auto a=*q.begin(),b=*(--q.end());
        q.erase(q.begin());
        q.erase(--q.end());
        int c=(b.second-1)/a.second+1,d=c*a.second-b.second;
        string s=a.first,t=b.first;
        for(int i=1;i<c;i++)s+=t;
        if(d)q[s]=d;
        if(a.second-d)q[s+t]=a.second-d;
    }
    auto x=*q.begin();
    while(x.second--)cout<<x.first;
}