#include <map>
#include <set>
#include <list>
#include <cmath>
#include <queue>
#include <stack>
#include <cstdio>
#include <string>
#include <vector>
#include <complex>
#include <cstdlib>
#include <cstring>
#include <numeric>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <functional>
 
#define mp       make_pair
#define pb       push_back
#define all(x)   (x).begin(),(x).end()
#define rep(i,n) for(int i=0;i<(n);i++)
 
using namespace std;
 
typedef    long long          ll;
typedef    unsigned long long ull;
typedef    vector<bool>       vb;
typedef    vector<int>        vi;
typedef    vector<vb>         vvb;
typedef    vector<vi>         vvi;
typedef    pair<int,int>      pii;
 
const int INF=1<<29;
const double EPS=1e-9;
 
const int dx[]={1,0,-1,0},dy[]={0,-1,0,1};
int main(int argc, char const *argv[]) {
	int N;
	cin >> N;
	std::vector<string> s;

	for (int i = 0; i < N; ++i) {
		string tmp;
		cin >> tmp;
		s.push_back(tmp);
	}
	sort(s.begin(), s.end());
	bool flag = true;
	string T;
	while(flag) {
		flag = false;
		char c = 'z' + 1;
		int ci = 0;
		for (int i = 0; i < N; ++i) {
			if (s[i].size() == 0) continue;
			if (c > s[i][0] || (c == s[i][0] && s[i].size() > s[ci].size())) {
				ci = i;
				c = s[i][0];
				flag = true;
			}
		}
		if (flag) {
			s[ci] = s[ci].substr(1);
			//cout << "debug" << s[ci] << endl;
			T += c;
		}
	}
	cout << T << endl;

	return 0;
}