#include <iostream>
#include <cstdio>
#include <math.h>
#include <algorithm>
#include <vector>
#include <cstring>
#include <iomanip>
#include <map>
#include <set>

#define F first
#define S second

using namespace std;

//const unsigned long long m = 2971215073;
const unsigned long long pp = 1031;
const unsigned long long pp1 = 237;

//vector <unsigned long long> a1, a2, h1, h2, p;
unsigned long long a1[100009], a2[100009];
pair <unsigned long long, unsigned long long> h1[100009], h2[100009], p[100009];
//set <pair <unsigned long long, unsigned long long> > t;
pair <unsigned long long, unsigned long long> t[100009];
unsigned long long n;
pair <long long, long long> ans = make_pair(-1, -1);

pair <unsigned long long, unsigned long long> has(unsigned long long l, unsigned long long r, bool s)
{
    if (!s)
       // return (((h1[r] - ((((!l ? 0 : h1[l - 1]) * p[r - l + 1]) % m) + m) % m) % m) + m) % m;
        return make_pair(h1[r].F - (!l ? 0 : h1[l - 1].F) * p[r - l + 1].F, h1[r].S - (!l ? 0 : h1[l - 1].S) * p[r - l + 1].S);
    else
        //return (((h2[r] - ((((!l ? 0 : h2[l - 1]) * p[r - l + 1]) % m) + m) % m) % m) + m) % m;
        return make_pair(h2[r].F - (!l ? 0 : h2[l - 1].F) * p[r - l + 1].F, h2[r].S - (!l ? 0 : h2[l - 1].S) * p[r - l + 1].S);
}

bool f(long long k)
{
    //t.clear();
    pair<unsigned long long, unsigned long long> h;
    for (long long i = 0; i + k < n; i++)
    {
        //cout << i << " " << k << endl;
        h = has(i, i + k, 0);
        //t.insert(h);
        t[i] = h;
        //else
    }

    sort(t, t + n - k + 1);

//    for (set<unsigned long long>::const_iterator it = t.begin(); it != t.end(); ++it)
  //      cout << *it << " ";
    //cout << endl;

    for (long long i = 0; i + k < n; i++)
    {
        h = has(i, i + k, 1);
        //t.insert(h);
        //cout << h << " ";

        //if (t.find(h) != t.end())

        if (t[lower_bound(t, t + n - k + 1, h) - t] == h)

        //if (t.size() == r)
        {
            //cout << k  << " " << ans.F << endl;
            //if (k < ans.F)
              //  cout << "*" << endl;
            if (k > ans.F)
            {
                ans.F = k;
                ans.S = i;
            }
            return true;
        }

    }//cout << endl;

    return false;
}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    freopen("input.txt", "r", stdin);freopen("output.txt", "w", stdout);
    //freopen("floyd.in", "r", stdin);freopen("floyd.out", "w", stdout);


    cin >> n;

    //p.resize(n);
    //h1.resize(n);
    //h2.resize(n);

    char d;

    for (long long i = 0; i < n; i++)
    {
        cin >> d;
        //a1.push_back(d - 'A' + 1);
        a1[i] = d - 'A' + 1;
    }
    for (long long i = 0; i < n; i++)
    {
        cin >> d;
        //a2.push_back(d - 'A' + 1);
        a2[i] = d - 'A' + 1;
    }


   // p[0] = pp;
   p[0].F = 1;
   p[0].S = 1;
    for (long long i = 1; i < n; i++)
        //p[i] = (((p[i - 1] * pp) % m) + m) % m;
        p[i] = make_pair(p[i - 1].F * pp, p[i - 1].S * pp1);

  //  for (unsigned long long i = 0; i < n; i++)
    //    cout << p[i] << " ";

    h1[0] = make_pair(a1[0], a1[0]);
   // cout << h1[0] << " ";
    for (long long i = 1; i < n; i++)
    {
       // h1[i] = (((h1[i - 1] * pp + a1[i]) % m) + m) % m;
        h1[i] = make_pair(h1[i - 1].F * pp + a1[i], h1[i - 1].S * pp1 + a1[i]);
       // cout << h1[i] << " ";
    }

    h2[0] = make_pair(a2[0], a2[0]);
    for (long long i = 1; i < n; i++)
    {
        //h2[i] = (((h2[i - 1] * pp + a2[i]) % m) + m) % m;
        h2[i] = make_pair(h2[i - 1].F * pp + a2[i], h2[i - 1].S * pp1 + a2[i]);
    }
    long long l = -1, r = n, m = 0;
    while (l + 1 < r)
    {
        m = (l + r) / 2;
        if (f(m))
            l = m;
        else
            r = m;
    }

    //cout << ans.F << " " << ans.S << endl;

    for (long long i = ans.S; i <= ans.S + ans.F; i++)
        cout << (char)(a2[i] + 'A' - 1);

    return 0;
}