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