#include <fstream>
#include <string.h>

using namespace std;
ifstream fi("ordine.in");
ofstream fo("ordine.out");
///se rezolva simplu cu un countsort simplu combinat cu metoda ruseasca aka bruteforce aka minigun aka basina
int n,X[30],lc;
char S[1000009];
int main()
{
    fi>>S;
    n=strlen(S);
    for(int i=0;i<n;i++)
        X[S[i]-'a'+1]++;
    for(int i=0;i<n;i++)
    ///reconstruierea
    {
        for(int j=1;j<=26;j++)
            if(X[j]>0 && lc!=j)
            {
                X[j]--;
                lc=j;
                fo<<(char)('a'+j-1);
                break;
            }
    }
    return 0;
}