#include<string>
#include<algorithm>
#define MAXN 25

using namespace std;

struct t{
	string s;
}str[MAXN];

bool cmp(t s1,t s2){
	return s1.s<=s2.s;
}
int main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	
	int n;
	cin>>n;
	for(int i=1;i<=n;i++)
		cin>>str[i].s;
	sort(str+1,str+n+1,cmp);
	for(int i=n;i>=1;i--)
		cout<<str[i].s;
	return 0;
}