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) {
		        int idx = 0;
		        while (idx < s1.length() && idx < s2.length()) {
		            if (s1.charAt(idx) != s2.charAt(idx)) {
		                return s1.charAt(idx) - s2.charAt(idx);
		            }
		            idx++;
		        }
		        return s2.length() - s1.length();
		    }
 		});
		for (int i = 0; i < n; i++) {
		    queue.add(new StringBuilder(sc.next()));
		}
		StringBuilder sb = new StringBuilder();
		while (queue.size() > 0) {
		    StringBuilder out = queue.poll();
		    sb.append(out.charAt(0));
		    out.deleteCharAt(0);
		    if (out.length() > 0) {
		        queue.add(out);
		    }
		}
		System.out.println(sb);
	}
}