#include<iostream>
#include<cstring>
#include<algorithm>
#include<cstdio>
using namespace std;
#define maxn 25
int n;
string s[maxn],str;
int main(void)
{
	cin>>n;
	for(int i=1;i<=n;++i)
	 cin>>s[i];
	sort(s+1,s+n+1);
	for(int i=n;i>=1;--i)
	 str+=s[i];
	cout<<str<<endl;
}