contain_us_all

// by: Emiso
#include <bits/stdc++.h>
#define MAX 10007
#define ALP 26

using namespace std;
typedef pair<int, int> pii;
typedef long long ll;
int C(char c) { return c - 'A'; }

struct aho {
    int parent[MAX], suffix[MAX], to[MAX][ALP], super[MAX];
    char from[MAX];
    int id[MAX], cnt, built;
    long long ending[MAX], lazy[MAX];

    int new_node(int _parent = 0, char _from = ' ') {
        parent[cnt] = _parent; from[cnt] = _from; id[cnt] = -1;
        suffix[cnt] = super[cnt] = ending[cnt] = lazy[cnt] = 0;
        for(int i = 0; i < ALP; i++) to[cnt][i] = 0;
        return cnt++;
    }

    aho() {
        cnt = built = 0;
        new_node();
    }

    int add(string &word, int _id = 0) {
        int node = 0;
        for(int i = 0; i < word.size(); i++) {
            int nxt = C(word[i]);
            if(!to[node][nxt]) to[node][nxt] = new_node(node, word[i]);
            node = to[node][nxt];
        }
        ending[node] |= _id;
        if(id[node] == -1) id[node] = _id;
        return id[node];
    }

    void build() {
        built = 1;
        queue<int> q;
        for(int i = 0; i < ALP; i++)
            if(to[0][i]) q.push(to[0][i]);

        while(!q.empty()) {
            int v = q.front(); q.pop();
            if(parent[v]) suffix[v] = to[suffix[parent[v]]][C(from[v])];

            if(id[v] != -1) super[v] = v;
            else super[v] = super[suffix[v]];

            ending[v] |= ending[suffix[v]];
            for(int i = 0; i < ALP; i++) {
                if(!to[v][i]) to[v][i] = to[suffix[v]][i];
                else q.push(to[v][i]);
            }
        }
    }

} dict;

char st[57];
int n;
pii p[MAX][1 << 12];
int vis[MAX][1 << 12];

void print(pii a){
    string ans = "";
    while(a.first != 0) { ans += dict.from[a.first]; a = p[a.first][a.second]; }
    reverse(ans.begin(), ans.end());
    printf("%s\n", ans.c_str());
}
void bfs(){
    queue<pii> q;
    q.push({0, 0});
    vis[0][0] = 1;
    pii actual;
    while(!q.empty()){
        actual = q.front();
        q.pop();
        if(actual.second == (1 << n)-1) { print(actual); return; }
        for(int i = 0; i < 26; i++){
            int prox = dict.to[actual.first][i];
            int bit = (actual.second | dict.ending[prox]);
            if(vis[prox][bit]) continue;
            vis[prox][bit] = 1;
            p[prox][bit] = actual;
            q.push({prox, bit});
        }
    }
}
int main() {
    scanf("%d", &n);

    for(int i = 0; i < n; i++) {
        scanf(" %s", st);
        string s(st);
        dict.add(s, 1 << i);
    }
    dict.build();
    bfs();
    return 0;
}