#include <bits/stdc++.h>

using namespace std;

using ll = long long;
using ul = unsigned long;
using ull = unsigned long long;

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

	const string G{ 'z' + 1 };
	int n;
	cin >> n;
	priority_queue<string, vector<string>, greater<string> > pq;
	for (int i = 0; i < n; ++i)
	{
		string s;
		cin >> s;

		pq.push(s + G);
	}

	stringstream ss;
	while (!pq.empty())
	{
		string s = pq.top();
		ss << s[0];
		pq.pop();
		if (s.size() > 1 && s.substr(1) != G)
			pq.push(s.substr(1));
	}
	cout << ss.str() << "\n";

	return 0;
}