#include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <list>
#include <stack>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <algorithm>
#include <functional>
#include <limits>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <climits>
#include <complex>

using namespace std;

#define INF (INT_MAX/3)
#define PI (2*acos(0.0))
#define EPS (1e-8)

typedef long long ll;
typedef unsigned long long ull;

int main(){
  ios_base::sync_with_stdio(0);
  int N, size = 0, max_size = 0;
  cin >> N;
  vector<string> S(N);
  for(int i = 0; i < N; i++){
    cin >> S[i];
    size += S[i].size();
    if(S[i].size() > max_size) max_size = S[i].size();
  }

  for(int i = 0; i < N; i++){
    for(int j = 0; j < (max_size - S[i].size()); j++) S[i] += "~";
  }

  string T("");

  while(size--){
    sort(S.begin(), S.end());
    T += S[0][0];
    S[0].erase(S[0].begin());
    S[0] += "~";
    if(S[0] == "") S.erase(S.begin());
  }

  cout << T << endl;
  return 0;
}