#include<cstring>
#include<iostream>
#include<cstdio>

#include<algorithm>
using namespace std;
int main()
{
    int n;
   while(cin>>n,n!=0)
     { 
         string a[n];
         int location=-1;
        for (int i = 0; i < n; i++) {
            cin >> a[i];
        }
        if(n==1) {cout<<a[0];return 0;}//*****n=1时直接输出就可
        for(int i=0;i< n-1;i++)
        {
            if(n==1) {string f=a[0];location=f.size();cout<<location;break;}
            string b ,c;
            b=a[i];c=a[(i+1)%n];
            reverse(b.begin(),b.end());
            reverse(c.begin(),c.end());
            int current_location=-1;
            for(int j=0;j<min(b.size(),c.size());j++)
            {
                if(b[j]==c[j]) current_location=j;
                else break;
            }
            if(current_location<location||location==-1)//寻找最短前缀输出
            {
                location=current_location;
            }

        }
        if(location<0) cout<<endl;
        else 
        {
            string result =a[0];
            reverse(result.begin(),result.end());
            result =  result.substr(0,location+1);
            reverse(result.begin(),result.end());
            cout<<result<<endl;
        }
   }
}