#include<bits/stdc++.h>
using namespace std;
string s;
int main(){
    cin>>s;
    vector<char> s2;
    int j=0;
    for(int i=0;i<s.size();i++){
        if(s[i]>='0'&&s[i]<='9'){
            s2.push_back(s[i]);
        }
    }
    sort(s2.begin(),s2.end());
    for(int i=s2.size()-1;i>=0;i--){
        cout<<s2[i];
    }
    return 0;
}