#define _USE_MATH_DEFINES
#include <algorithm>
#include <cstdio>
#include <functional>
#include <iostream>
#include <cfloat>
#include <climits>
#include <cstring>
#include <cmath>
#include <fstream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <time.h>
#include <vector>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;
typedef pair<ll, int> ll_i;
typedef pair<double, int> d_i;
typedef pair<ll, ll> ll_ll;
typedef pair<double, double> d_d;
struct edge { int v, w; };

ll MOD = 1000000007;
ll _MOD = 1000000009;
double EPS = 1e-10;

int main() {
	int N; cin >> N;
	vector<string> S(N);
	for (int i = 0; i < N; i++) {
		cin >> S[i];
		S[i].push_back('~');
	}
	string T;
	for (;;) {
		int i = 0;
		for (int j = 0; j < N; j++)
			if (S[j] < S[i])
				i = j;
		if (S[i][0] == '~') break;
		T.push_back(S[i][0]);
		S[i].erase(S[i].begin());
	}
	cout << T << endl;
}