#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>
#include <fstream>
#include <queue>
#include <complex>

#define INF_MIN 100000000
#define INF 1145141919
#define INF_MAX 2147483647
#define LL_MAX 9223372036854775807
#define EPS 1e-10
#define PI acos(-1)
#define LL long long

using namespace std;

#define MAX_N 51

int N;

string str[MAX_N];

priority_queue<string, vector<string>, greater<string> > que;

int main(){

  cin >> N;
  for(int i = 0; i < N; i++){
    cin >> str[i];
    str[i] += 'z' + 1;
    que.push(str[i]);
  }

  stringstream ans;

  while(que.size()){

    string S = que.top();
    que.pop();

    ans << S[0];
    S.erase(0,1);
    if(S.length() > 1)
      que.push(S);

  }

  cout << ans.str() << endl;

  return 0;

}