#include <bits/stdc++.h>

using namespace std;

int main(void)
{
	cin.tie(0);
	ios::sync_with_stdio(false);

	string res,s;
	vector <string> v;
	int n;
	priority_queue <pair<pair<char,int>, pair<int, int>>, vector<pair<pair<char,int>, pair<int, int>>>, greater<pair<pair<char,int>, pair<int, int>>>> pque;

	cin >> n;

	for (int i = 0; i < n; i++)
	{
		cin >> s;
		v.push_back(s);
	}

	for (int i = 0; i < n; i++)
	{
		pque.push(make_pair(make_pair(v[i][0],0), make_pair(i, 0)));
	}

	while (!pque.empty())
	{
		char ch = pque.top().first.first;
		int num = pque.top().first.second;
		int now = pque.top().second.first;
		int idx = pque.top().second.second;
		pque.pop();
		res += ch;

		if (idx + 1 < v[now].length())
		{
			pque.push(make_pair(make_pair(v[now][idx + 1],idx+1), make_pair(now, idx + 1)));
		}
	}

	cout << res << '\n';

	return 0;
}