#include <iostream>
#include <vector>
#include <cstdio>
#include <sstream>
#include <map>
#include <string>
#include <algorithm>
#include <queue>
#include <cmath>
#include <set>
using namespace std;

int main(){
	int n;
	cin >> n;
	vector<string> s(n);
	for(int i=0; i<n; i++){
		cin >> s[i];
		s[i].resize(50, '{');
	}

	string ans = "";
	priority_queue<string, vector<string>, greater<string>> pq(s.begin(), s.end());
	while(pq.size()){
		string tmp = pq.top(); pq.pop();
		ans += tmp[0];
		if(tmp.size() > 1 && tmp[1] != '{'){
			tmp = tmp.substr(1,string::npos) + "{";
			pq.push(tmp);
		}
	}

	cout << ans << endl;


	return 0;
}