#include<cstdio>
#include<cstring>
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(j=i=0;i<26&&!j;i++)
if(x[i])
     j=1,s[0]=i+'a',x[i]--;
for(i=1;i<n;i++)
     {for(k=-1,j=0;j<26;j++)
     if(2*x[j]>n-i&&s[i-1]!=j+'a')
           k=j;
     if(k>-1)
           s[i]=k+'a',x[k]--;
     else
           for(j=l=0;l<26&&!j;l++)
           if(s[i-1]!=l+'a'&&x[l])
                 j=1,s[i]=l+'a',x[l]--;}
puts(s);  
return 0;}