#include"bits/stdc++.h"

//#include<bits/stdc++.h>
using namespace std;
#define print(x) cout<<x<<endl;
#define rep(i,a,b) for(int i=a;i<b;i++)
#define REP(i,a) for(int i=0;i<a;i++)
typedef long long ll;
typedef pair<int, int> PI;
typedef pair<int, PI> V;
const ll mod = 10000000000;

int main() {
	int n;
	string s[52];
	cin >> n;
	REP(i, n) {	cin >> s[i];}
	string ans="";
	while (true) {
		char m='z';
		int mi=-1;
		REP(i, n) {
			if (s[i].empty())continue;
			if (m == 'z'||m > s[i].front()) {
				m = s[i].front();
				mi = i;
			}
			else if (m == s[i].front()) {
				int j = 0;
				while (true) {
					if (j == s[mi].size() || j == s[i].size())break;
					if (s[mi][j] != s[i][j]) {
						mi = s[mi][j] > s[i][j] ? i:mi;
						break;
					}
					j++;
				}
			}
		}
		if (mi == -1)break;
		ans += m;
		s[mi].erase(s[mi].begin() + 0);
	}
	print(ans);
	return 0;
}