#include<stdio.h>
#include<string.h>
int i,n,x[26],j,k,l;
char s[1000001];
int main() {
    freopen("ordine.in","r",stdin),freopen("ordine.out","w",stdout),gets(s),n=strlen(s);
    for(i=0;i<n;i++)
        x[s[i]-'a']++;
    for(i=0;i<n;i++) {
        for(k=-1,j=0;j<26;j++)
        if(2*x[j]>n-i)
            k=j;
        if(k>-1)
            s[i]=k+'a',x[k]--;
        else
            for(j=l=0;l<26&&!j;l++)
            if(((i&&s[i-1]!=l+'a')||!i)&&x[l])
                j=1,s[i]=l+'a',x[l]--;
    }
    puts(s);
}