#include<iostream>
#include<string>
#include<algorithm>
#include<functional>
#include<vector>
#include<stack>
#include<queue>
#include<set>
#include<map>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
using namespace std;

multiset<string> dict;

signed main()
{
	int n, i, j;
	int sumLen = 0;
	
	string s;
	cin >> n;
	for( i = 0; i < n; i++ ) {
		cin >> s;
		sumLen += s.length();
		for( j = s.length(); j < 100; j++ )
			s += char('z' + 1);
		dict.insert(s);
	}
	
	for( i = 0; i < sumLen; i++ ) {
		multiset<string>::iterator it = dict.begin();
		string cpy = *it;
		cout << cpy[0];
		string dist;
		
		for(int j = 1; j < cpy.length(); j++)
			dist += cpy[j];
		dist += (char)('z' + 1);
		
		dict.erase(it);
		dict.insert(dist);
	}
	return 0;
}