package no205;

import java.util.PriorityQueue;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		PriorityQueue<String> pq = new PriorityQueue<>();
		for(int i=0;i<n;i++) {
			pq.add(sc.next() + "{");
		}
		StringBuilder ans = new StringBuilder();
		while(!pq.isEmpty()) {
			String min = pq.poll();
			ans.append(min.charAt(0));
			if (min.length() > 2) {
				pq.offer(min.substring(1));
			}
		}
		System.out.println(ans.toString());
	}

}