#include<iostream>

#include<cstring>

#include<cstdio>

#include<cmath>

using namespace std;

struct node

{

    node* next[];

    bool end;

    int num;

    node()

    {

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

            next[i] = NULL;

        end = ;

        num = ;

    }

};

node* root;

char s[],ma[];

int mx;

int insert()

{

    int l =strlen(s);

    node* k = root;

    int i,j;

    for(i = ;i<l-;i++)

    {

        int id = s[i]-'a';

        if(k->next[id] == NULL)

        {

            node* t = new node();

            k->next[id] = t;

            k = k->next[id];

        }

        else

        {

            k = k->next[id];

        }

    }

    int id = s[i]-'a';

    if(k->next[id] == NULL)

    {

        node* t = new node();

        t->end = ,t->num = ;

        k->next[id] = t;

        k = k->next[id];

    }

    else

    {

        k = k->next[id];

        k->num++;

    }

    return k->num;

}

int main()

{

    int n,i,j,k;

    while(cin>>n,n)

    {

        root = new node();

        mx = ;

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

        {

            cin>>s;

            int t = insert();

            if(mx<t)

            {

                mx = t;

                int l = strlen(s);

                for(j = ;j<=l;j++)

                    ma[j] = s[j];

            }

        }

        cout<<ma<<endl;

    }

    return ;

}