/*
ID: Sho10
LANG: C++
TASK:
*/
#include <bits/stdc++.h> //JuniorMonster a.k.a Sho10
#define ll long long int
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#define all(a) (a).begin(), (a).end()
#define sz size
#define f first
#define s second
#define pb push_back
#define er erase
#define in insert
#define mp make_pair
#define pi pair
#define rc(s) return cout<<s,0
#define endl '\n'
#define mod 1000000007
#define PI 3.14159265359
#define CODE_START  ios_base::sync_with_stdio();cin.tie();cout.tie();
using namespace std;
ll n;
string s;
map<ll,ll>m;
int32_t main(){
CODE_START;
ifstream cin("ordine.in");
ofstream cout("ordine.out");
cin>>s;
n=s.size();
for(ll i=0;i<s.size();i++)
{
    m[s[i]-'a']++;
}
for(ll i=0;i<s.size();i++)
{
    if(i==0){
        for(ll j=0;j<=26;j++)
        if(m[j]>=1){
                m[j]--;
        s[i]=j+'a';
        break;
    }
}else {
for(ll j=0;j<=26;j++)
{
    if(m[j]>=1&&s[i-1]-'a'!=j){
        s[i]=j+'a';
        m[j]--;
break;
    }
}
}
}
cout<<s<<endl;
}