#include <bits/stdc++.h>

using namespace std;

typedef vector<int> vi;
typedef pair<int, int> pii;
typedef long long ll;

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n)  FOR(i,0,n)
#define INF 1e9

int main(){
    vector<pair<string,int> > strs;
    int N;
    size_t max_length = 0;
    vector<size_t> str_lengths;
    cin >> N ;
    vector<int> erase_count(N,0);
    
    for(int i=0;i<N;i++){
        string str;
        cin >> str ;
        strs.push_back(make_pair(str,i));
        str_lengths.push_back(str.length());
        max_length = max(max_length,str.size());
    }

    FOR(i, 0, N){
        size_t l = strs[i].first.length();
        if(l < max_length){
            FOR(j,0,max_length -l)
                strs[i].first += strs[i].first[l-1];
        }
    }



    string ans="";
    while(!strs.empty()){
        sort(strs.begin(),strs.end());
        ans.insert(ans.end(),*strs[0].first.begin());
        strs[0].first.erase(strs[0].first.begin());
        strs[0].first += strs[0].first[strs[0].first.length()-1];
        erase_count[strs[0].second]++;
        if(erase_count[strs[0].second] == str_lengths[strs[0].second]){
            strs.erase(strs.begin());
        }
    }
    cout << ans << endl;

    return 0;
}