#include "bits/stdc++.h"
using namespace std;
#ifdef _DEBUG
#include "dump.hpp"
#else
#define dump(...)
#endif

//#define int long long
#define rep(i,a,b) for(int i=(a);i<(b);i++)
#define rrep(i,a,b) for(int i=(b)-1;i>=(a);i--)
#define all(c) begin(c),end(c)
const int INF = sizeof(int) == sizeof(long long) ? 0x3f3f3f3f3f3f3f3fLL : 0x3f3f3f3f;
const int MOD = 1'000'000'007;
template<class T> bool chmax(T &a, const T &b) { if (a < b) { a = b; return true; } return false; }
template<class T> bool chmin(T &a, const T &b) { if (b < a) { a = b; return true; } return false; }

signed main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	int N; cin >> N;
	vector<string> v(N); rep(i, 0, N) {
		cin >> v[i];
	}
	priority_queue<string, vector<string>, greater<string>> pq;
	rep(i, 0, N)pq.push(v[i]);
	string ans = "";
	while (pq.size()) {
		string t = pq.top(); pq.pop();
		ans += t.front();
		t = t.substr(1);
		if (t.size())
			pq.push(t);
	}
	cout << ans << endl;
	return 0;
}