#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
using namespace std;
int n;
void dfs(int x);
struct hehe
{
	char str[100];
}q[100];
int w[10]={0};
int answer=0;
char ans[1000];
char ans1[1010];
int la;
bool used[10]={0};
int main()
{
	freopen ("substring.in","r",stdin);
	freopen ("substring.out","w",stdout);
	cin>>n;
	for (int i=0;i<n;i++)
	{
		cin>>q[i].str;
	}
	dfs(1);
	cout<<ans;
	return 0;
}
 
void dfs(int x)
{
	if (x==n+1)
	{
		if (!answer)
		{
			for (int i=1;i<=n;i++)
			{
				for (int j=0;j<strlen(q[w[i]].str);j++)
				{
					ans[la]=q[w[i]].str[j];
					la++;
				}
			}
			answer++;
		}
		else
		{
			int a=0;
			for (int i=1;i<=n;i++)
			{
				for (int j=0;j<strlen(q[w[i]].str);j++)
				{
					ans1[a]=q[w[i]].str[j];
					a++;
				}
			}
			if (strcmp(ans,ans1)>0)
			{
				for (int i=0;i<la;i++)
				{
					ans[i]=ans1[i];
				}
			}
		}
	}
	else
	{
		for (int i=0;i<n;i++)
		{
			if (!used[i])
			{
				w[x]=i;
				x++;
				used[i]=1;
				dfs(x);
				x--;
				used[i]=0;
			}
		}
	}
}