import java.util.*;

public class Main {
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		PriorityQueue<StringBuilder> queue = new PriorityQueue<>();
		while (0 < n--) {
		    StringBuilder sb = new StringBuilder(sc.next());
		    sb.append('A');
		    queue.add(sb);
		}
		StringBuilder ans = new StringBuilder();
		while (queue.size() > 0) {
		    StringBuilder sb = queue.poll();
		    ans.append(sb.charAt(0));
		    sb.deleteCharAt(0);
		    if (sb.length() > 1) {
		        queue.add(sb);
		    }
		}
		System.out.println(ans);
	}
}