#include <fstream>
#include <algorithm>
#include <string>
#include <cstring>

using namespace std;

ifstream fin("substring.in");
ofstream fout("substring.out");

const int maxn = 8 + 2;
const int maxlstr = 100 + 10;
int n;

class poi
{
    public:
		string s;
}str[maxn*maxlstr];

void fswap(string &a, string &b)
{
	string temp = a;
	a = b;
	b = temp;
	//fout<<a<<endl<<b<<endl<<temp<<endl;
	return ;
}
int main()
{
	fin>>n;;
	for(int i=1;i<=n;i++)
		fin>>str[i].s;
	for(int i=1;i<=n;i++)
		for(int j=1;j<=n-i;j++)
		{
			if(str[j].s+str[j+1].s>str[j+1].s+str[j].s)
				fswap(str[j].s, str[j+1].s);
		}
	for(int i=1;i<=n;i++)
		fout<<str[i].s;
	fin.close();
	fout.close();
	
	return 0;
}