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<StringBuilder>(new Comparator<StringBuilder>() {
		    public int compare(StringBuilder s1, StringBuilder s2) {
		        if (s1.charAt(0) == s2.charAt(0)) {
		            if (s1.length() == 1) {
		                return 1;
		            } else if (s2.length() == 1) {
		                return -1;
		            } else {
		                return s1.compareTo(s2);
		            }
		        } else {
		            return s1.charAt(0) - s2.charAt(0);
		        }
		    }
		});
		while (0 < n--) {
		    queue.add(new StringBuilder(sc.next()));
		}
		StringBuilder ans = new StringBuilder();
		while (queue.size() > 0) {
		    StringBuilder sb = queue.poll();
		    ans.append(sb.charAt(0));
		    sb.deleteCharAt(0);
		    if (sb.length() > 0) {
		        queue.add(sb);
		    }
		}
		System.out.println(ans);
	}
}