#include<bits/stdc++.h>
using namespace std;
int main(){
    string w;
    map<int,string>m;
    while(cin>>w){
        if(w.find('-')!=string::npos){
            cout<<"Invalid input";
            return 0;
        }
        for (char c:w)
        if(isdigit(c))
        m[c-'0'] + = w. erase (w. find(c),1);
    }
    for(auto&i:m)
    cout<<i.second<<"";
}