#include <iostream>

using namespace std;

const int N = 200;

int n;
string str[N];

int main()
{
    while (cin >> n, n)
    {
        int len = 1000;
        for (int i = 0; i < n; i ++ )
        {
            cin >> str[i];
            if (len > str[i].size()) len = str[i].size();
        }

        while (len)
        {
            bool success = true;
            for (int i = 1; i < n; i ++ )
            {
                bool is_same = true;
                for (int j = 1; j <= len; j ++ )
                    if (str[0][str[0].size() - j] != str[i][str[i].size() - j])
                    {
                        is_same = false;
                        break;
                    }
                if (!is_same)
                {
                    success = false;
                    break;
                }
            }

            if (success) break;
            len -- ;
        }

        cout << str[0].substr(str[0].size() - len) << endl;
    }

    return 0;
}