#include <iostream>
#include <string>
#include <vector>
#include <set>
#include <algorithm>
using namespace std;

int main()
{
	int n;
	cin >> n;
	vector<string> vs;
	vs.resize(n);
	for (int i = 0; i < n; i++) {
		cin >> vs[i];
		vs[i]+=("\xff");
	}
	sort(vs.begin(), vs.end());
	string t;
	while (vs.size()) {
		t.push_back(vs[0].front());
		vs[0].erase(vs[0].begin());
		if (vs[0]=="\xff") vs.erase(vs.begin());
		sort(vs.begin(), vs.end());
	}

	cout << t << endl;

    return 0;
}