#pragma GCC optimize("Ofast")
//#pragma GCC target("avx")
#pragma GCC optimize ("unroll-loops")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace __gnu_pbds;
using namespace std;

#define fi first
#define se second
#define pb push_back
#define sz(x)  ((int)x.size ())
#define all(x) (x).begin(), (x).end()
#define re return
#define mp make_pair
#define sqrt(x) sqrt (abs(x))
#define y0 y3451
#define y1 y4562
#define j0 j25624
#define j1 j45624
#define makeunique(x) sort(all(x)), (x).resize (unique(all(x)) - (x).begin())
#define dbg2(x, y) cout << x << " " << y << endl;
#define dbg3(x, y, z) cout << x << " " << y  << " " << z << endl;
#define rep(i, n) for (int i = 0; i < (n); i++)
#define rrep(i, n) for (int i = (n) - 1; i >= 0; i--)

typedef pair <int, int> ii;
typedef long long ll;
typedef unsigned long long ull;
typedef double D;
typedef long double ld;
typedef unsigned int uint;
typedef vector <string> vs;
typedef vector <int> vi;
typedef vector <ii> vii;
typedef vector <vi> vvi;

template <class T> using _tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template <class T> T abs (T x) { re x > 0 ? x : -x; }
template <class T> T sqr (T x) { re x * x; }
template <class T> T gcd (T a, T b) { re a ? gcd (b % a, a) : b; }
template <class T> int sgn (T x) { re x > 0 ? 1 : (x < 0 ? -1 : 0); }

#define filename ""

const D pi = acos(-1.);
const int N = 1e5 + 12000;
const int inf = 1e9 + 7;

int n, m;
int cnt = 1;
int to[N][30];
int gt[N][30];
int link[N];
int pr[N];
int pc[N];
string s[N];
int ok[N];
vii g[N];
int ww[N];

int dp[5000][5000];
char pred[5000][5000];
int prm[5000][5000];

void add(string& s, int z) {
	int cur = 0;
	for (auto x : s) {
		int z = (int) x - 'A';
		if (to[cur][z] == -1) {
			to[cur][z] = cnt;
			gt[cur][z] = cnt;
			pr[cnt] = cur;
			pc[cnt] = z;
			cnt++;
		}
		cur = to[cur][z];
	}
	ok[cur] |= (1 << z);
}

int go(int v, int c) {
	if (gt[v][c] != -1) re gt[v][c];
	if (v == 0) re 0;
	re gt[v][c] = go(link[v], c);
}


int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
	memset(gt, -1, sizeof(gt));
	memset(to, -1, sizeof(to));
	memset(dp, -1, sizeof(dp));

	cin >> n;
	for (int i = 0; i < n; i++) {
		cin >> s[i], add(s[i], i);
	}
	queue<int> q;
	q.push(0);
	while(!q.empty())  {
		int best = q.front();
		q.pop();
		ww[best] = ok[best];
		if (best != 0 && pr[best] != 0) {
			link[best] = go(link[pr[best]], pc[best]);
		}
		ww[best] |= ww[link[best]];
		for (int i = 0; i < 26; i++)
			if (to[best][i] != -1)
				q.push(to[best][i]);
	}
	dp[0][ok[0]] = 0;
	pred[0][ok[0]] = 0;
	queue<pair<int, int>> qq;
	qq.push({0, ok[0]});
	ii ans = {-1, -1};
	while (!qq.empty()) {
		auto best = qq.front();
		qq.pop();
		int cur = best.fi;
		int curm = best.se;
		if (__builtin_popcount(curm) == n) {
		 	ans = mp(cur, curm);
		 	break;
		}
		for (int i = 0; i < 26; i++) {
			int nxt = go(cur, i);
			int newm = curm | ww[nxt];
			if (dp[nxt][newm] == -1) {
				dp[nxt][newm] = cur;
				prm[nxt][newm] = curm;
				pred[nxt][newm] = (char) (i + 'A');
				qq.push({nxt, newm});
			}
		}
	}
	string hh = "";
	while (dp[ans.fi][ans.se] != ans.fi) {
		hh += pred[ans.fi][ans.se];
		ii tmp = ans;
		ans.fi = dp[tmp.fi][tmp.se];
		ans.se = prm[tmp.fi][tmp.se];
	}
	reverse(all(hh));
	cout << hh ;

	return 0;
}