#include<bits/stdc++.h>

 #define endl '\n'

 using namespace std;

 bool cmp(string a,string b)

 {

     return a.size()<b.size();

 }

 int main() {

 //    ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);

     int n;

     while(cin >> n) {

         string s;

         vector<string>a;

         if(n == ) {

             cin >> s;

             int sz= s.size();

             vector<string>xx;

             s+=s;

            // cout << s << endl;

             for(int i = ; i < sz;i++) xx.push_back(s.substr(i,sz));//截取起点为i长度为sz的字串

             sort(xx.begin(),xx.end());

             for(int i = ; i < xx.size(); i++) cout <<xx[i]<<endl;

             cout << xx[] << endl;continue;

         }

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

             cin >> s;

             int sz = s.size();

             s += s;

             vector<string>b;

             for(int j = ; j < sz; j++){//断环为链

                 for(int k = ; k < ( << sz); k++) {//用枚举子集来表示序列

                     string t;

                     for(int p = ; p < sz; p++) {

                         if(k & ( << p)) {

                             t += s[j + p];

                         }

                     }

                     //cout << t << endl;

                     b.push_back(t);

                 }

                 //cout << endl;

             }

             sort(b.begin(),b.end());

             b.erase(unique(b.begin(),b.end()),b.end());//每一个串的子序列按照字典序排序并去重

             for(int j = ; j < b.size(); j++) {//把每一个串的子序列加入总的字符串里

                 a.push_back(b[j]);

             }

         }

         sort(a.begin(),a.end());//按照所有串的子序列

 //        for(int i = 0; i < a.size(); i++) cout << a[i] <<endl;

         int ct = , maxx = ;

         vector<string>c,d;

         for(int i = ; i < a.size(); i++) {

             if(a[i] == a[i- ]) ct++;

             else ct = ;

             if(ct == n) c.push_back(a[i]),maxx=max(maxx,(int)a[i].size());//n个串里的公共子序列

         }

 //        for(int i = 0; i < c.size(); i++) cout << c[i] <<endl;

         if(c.size() == ) {

             cout <<  << endl; continue;

         }

         for(int i =  ; i < c.size(); i++) {

             if(c[i].size() == maxx){

                 cout<<c[i]<<endl;break;

             }

         }

     }

     return ;

 }