#include <iostream>
#include <string>
#include <algorithm>
using namespace std;
string ss[1000];
int main()
{
	int n;
	cin >> n;
	for (int i = 0; i < n; i++)
		cin >> ss[i];
	sort(ss, ss + n, [](const string& l, const string& r) {
		int ls = l.size(), rs = r.size();
		int maxl = max(ls, rs) * 2;
		for (int i = 0; i < maxl; i++)
			if (l[i%ls] < r[i%rs]) return false;
			else if (l[i%ls] > r[i%rs]) return true;
			return true;
	});
	for (int i = 0; i < n; i++)
		cout << ss[i];
	return 0;
}