#include <bits/stdc++.h>

using namespace std;

typedef pair<string, int> P;

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	int n;
	cin >> n;
	vector<string> s(n);
	for (int i = 0; i < n; i++) cin >> s[i];
	priority_queue<P, vector<P>, greater<P> > pq;
	for (int i = 0; i < n; i++) {
		s[i] += '}';
		pq.push(P(s[i], i));
	}
	string ans = "";
	while (!pq.empty()) {
		P p = pq.top();
		pq.pop();
		ans += p.first[0];
		if (p.first.length() == 2) continue;
		pq.push(P(p.first.substr(1, p.first.length() - 1), p.second));
	}
	cout << ans << endl;
	return 0;
}