#include "bits/stdc++.h"
using namespace std;

int main() {
	int N;
	cin >> N;
	vector<string> S(N);
	int cnt = 0;
	for (int i = 0; i < N; i++)
	{
		cin >> S[i];
		cnt += S[i].size();
	}

	string ans = "";
	for (int t = 0; t < cnt; t++)
	{
		sort(S.begin(), S.end());
		for (int i = 0; i < S.size(); i++)
		{
			if (S[i] != ""){
				ans += S[i][0];
				string temp = "";
				for (int j = 1; j < S[i].size(); j++)
				{
					temp += S[i][j];
				}
				S[i] = temp;
				break;
			}
		}
	}
	cout << ans << endl;
	cin >> ans;
	

}