import java.io.*;
import java.util.*;
import java.util.stream.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        PriorityQueue<MyString> queue = new PriorityQueue<>();
        for (int i = 0; i < n; i++) {
            queue.add(new MyString(sc.next().toCharArray()));
        }
        StringBuilder sb = new StringBuilder();
        while (queue.size() > 0) {
            MyString x = queue.poll();
            sb.append(x.getChar());
            if (!x.isEnd()) {
                queue.add(x);
            }
        }
        System.out.println(sb);
    }
    
    static class MyString implements Comparable<MyString> {
        char[] values;
        int current = 0;
        
        public MyString(char[] values) {
            this.values = values;
        }
        
        public int compareTo(MyString another) {
            for (int i = 0; i + current < values.length && i + another.current < another.values.length; i++) {
                if (values[current + i] != another.values[another.current + i]) {
                    return values[current + i] - another.values[another.current + i];
                }
            }
            return - (values.length - current) + (another.values.length - another.current);
        }
        
        public char getChar() {
            return values[current++];
        }
        
        public boolean isEnd() {
            return current == values.length;
        }
    }
}
class Utilities {
    static String arrayToLineString(Object[] arr) {
        return Arrays.stream(arr).map(x -> x.toString()).collect(Collectors.joining("\n"));
    }
    
    static String arrayToLineString(int[] arr) {
        return String.join("\n", Arrays.stream(arr).mapToObj(String::valueOf).toArray(String[]::new));
    }
}
class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public int[] nextIntArray() throws Exception {
        return Stream.of(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray();
    }
    
    public String next() throws Exception {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
    
}