#include <map>
#include <set>
#include <list>
#include <cmath>
#include <queue>
#include <stack>
#include <cstdio>
#include <string>
#include <vector>
#include <complex>
#include <cstdlib>
#include <cstring>
#include <numeric>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <functional>
  
#define mp       make_pair
#define pb       push_back
#define all(x)   (x).begin(),(x).end()
#define rep(i,n) for(int i=0;i<(n);i++)
  
using namespace std;
  
typedef    long long          ll;
typedef    unsigned long long ull;
typedef    vector<bool>       vb;
typedef    vector<int>        vi;
typedef    vector<vb>         vvb;
typedef    vector<vi>         vvi;
typedef    pair<int,int>      pii;
  
const int INF=1<<29;
const double EPS=1e-9;
  
const int dx[]={1,0,-1,0,1,1,-1,-1},dy[]={0,-1,0,1,1,-1,-1,1};


int main() {
    int N;
    cin >> N;
    std::vector<string> v;
    int maxsize = 0;
    int sum = 0;
    for (int i = 0; i < N; i++) {
        string temp;
        cin >> temp;
        int n = temp.size();
        sum += n;
        maxsize = max(maxsize, n);
        v.push_back(temp);
    }
    for (int i = 0; i < N; i++) {
        string add(maxsize - v[i].size() + 1, 'z' + 1);
        v[i] += add;
    }
    string ans = "";
    for (int i = 0; i < sum; i++) {
        char minc = 'z' + 1;
        int mincj;
        int maxsize = 0;
        for (int j = 0; j < N; j++) {
            if (v[j][0] < minc || (v[j][0] == minc && v[j].size() > maxsize)) {
                minc = v[j][0];
                mincj = j;
                maxsize = v[j].size();
            }
        }
        ans += v[mincj][0];
        v[mincj] = v[mincj].substr(1, v[mincj].size() - 1);
    
    }
    cout << ans << endl;



    return 0;
}