#include <bits/stdc++.h>
using namespace std;
int n;
string a[25];
int main ()
{
	cin>>n;
	for (int i=1;i<=n;i++)
		cin>>a[i];
	sort (a+1, a+1+n);
	for (int i=n;i>=1;i--)
		cout<<a[i];
	return 0;
}

思路感觉没问题，求调