#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <cmath>
#include <iomanip>
#include <map>
using namespace std;
typedef long long LL;

const LL MOD=1000000000;

struct Comp{
    bool operator()(const string& s1, const string& s2){
        int i = 0;
        for(; i < s1.size() && i < s2.size(); i++){
            if(s1[i] < s2[i]) return true;
            else if(s1[i] > s2[i]) return false;
        }
        return s1.size() > s2.size();
    }
};

int main(){
    LL N;
    cin >> N;
    vector<string> s(N);
    string ans;
    for(int i = 0; i < N; i++){
        cin >> s[i];
    }

    while(true){
        sort(s.begin(), s.end(), Comp());
        if(s[0].empty()) break;
        ans += s[0][0];
        s[0] = s[0].substr(1);
    }
    cout << ans << endl;
    return 0;
}