using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Text;
using System.Text.RegularExpressions;
using System.Linq;
using System.IO;

class Program
{
    static void Main()
    {
        new Magatro().Solve();
    }
}

class Magatro
{
    private int N;
    private string[] S;
    private int Length = 0;

    private void Scan()
    {
        N = int.Parse(Console.ReadLine());
        S = new string[N];
        for (int i = 0; i < N; i++)
        {
            string line = Console.ReadLine();
            Length += line.Length;
            S[i] = line + (char)('z' + 1);
        }
    }

    private int Compare(string a, string b)
    {
        int l = Math.Min(a.Length, b.Length);
        for (int i = 0; i < l; i++)
        {
            if (a[i] > b[i])
            {
                return 1;
            }
            if (a[i] < b[i])
            {
                return -1;
            }
        }
        return a.Length.CompareTo(b.Length);
    }

    public void Solve()
    {
        Scan();
        string ans = "";
        for (int i = 0; i < Length; i++)
        {
            int index = 0;
            string min = S[0];
            for (int j = 1; j < N; j++)
            {

                if (Compare(min,S[j]) > 0)
                {
                    min = S[j];
                    index = j;
                }
            }
            ans += min[0];
            S[index] = min.Substring(1);
        }
        Console.WriteLine(ans);
    }
}