#include<bits/stdc++.h>

using namespace std;

string common(string s,string t) {

    int most = ;

    int len = min(s.length(), t.length());

    for (int i = ; i < len; i++) {

        if (s[i] == t[i])

            most++;

        else

            break;

    }

    return s.substr(, most);

}

int main() {

    int n;

    while (cin >> n) {

        if (!n) break;

        string s;

        cin >> s;

        reverse(s.begin(), s.end());

        n--;

        for (int i = ; i < n; i++) {

            string t;

            cin >> t;

            reverse(t.begin(), t.end());

            s = common(s, t);

        }

        reverse(s.begin(), s.end());

        cout << s << endl;

    }

    return ;

}