#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <iomanip>
#include <cmath>
#include <stdio.h>
#include <queue>
#include <deque>
#include <cstdio>
#include <set>
#include <map>
#include <bitset>
#include <stack>
#include <cctype>
using namespace std;
string s[55];
int main() {
	int n;
	cin >> n;
	priority_queue<string,vector<string>,greater<string>> q;
	for (int i = 0; i < n; i++) {
		cin >> s[i];
		q.push(s[i] + '{');
	}
	string ans = "";
	while (!q.empty()) {
		string s1 = q.top();
		q.pop();
		if (s1[0] != '{') {
			ans += s1[0];
			q.push(s1.substr(1, s1.size() - 1));
		}
	}
	cout << ans << endl;
}