B

#include <algorithm>
#include <iostream>
#include <array>
#include <vector>


using namespace std;

#define int long long
#pragma comment(linker,"/STACK:1000000000,1000000000")

const long long INF = 1e9 + 7;
const int MAXN = 2e5 + 10;
const int N = 1e5 + 10;

const int M1 = 1e9 + 123;
const int M2 = 1e9 + 321;
const int P1 = 22811;
const int P2 = 22699;
array<int, MAXN> power1, power2;

void init_pow() {
    power1[0] = 1;
    power2[0] = 1;
    for (int i = 1; i < MAXN; ++i) {
        power1[i] = (power1[i - 1] * P1) % M1;
        power2[i] = (power2[i - 1] * P2) % M2;
    }
}

void build_hash(string& s, vector<pair<int, int>>& h) {
    int n = s.size();
    h.resize(n + 1);
    h[0].first = 0;
    h[0].second = 0;

    for (int i = 0; i < n; ++i) {
        h[i + 1].first = (h[i].first + (s[i] - 'a' + 1) * power1[i]) % M1;
        h[i + 1].second = (h[i].second + (s[i] - 'a' + 1) * power2[i]) % M2;
    }
}

pair<int, int> get_hash(vector<pair<int, int>>& h, int pos, int len, int mx_pow = 0) {
    int h1 = h[pos + len].first - h[pos].first;
    int h2 = h[pos + len].second - h[pos].second;
    if (h1 < 0) {
        h1 += M1;
    }
    if (h2 < 0) {
        h2 += M2;
    }
    if (mx_pow != 0) {
        h1 = h1 * power1[mx_pow - (pos + len - 1)] % M1;
        h2 = h2 * power2[mx_pow - (pos - + len - 1)] % M2;
    }
    return make_pair(h1, h2);
}

bool is_equal(vector<pair<int, int>>& h_l, vector<pair<int, int>>& h_r, int start1, int start2, int len) {
    pair<int, int> d_l, d_r;
    d_l.first = ((h_l[start1 + len].first - h_l[start1].first + M1) * power1[start2]) % M1;
    d_l.second = ((h_l[start1 + len].second - h_l[start1].second + M2) * power2[start2]) % M2;

    d_r.first = ((h_r[start2 + len].first - h_r[start2].first + M1) * power1[start1]) % M1;
    d_r.second = ((h_r[start2 + len].second - h_r[start2].second + M2) * power2[start1]) % M2;

    return d_l == d_r;
}

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);

    int n;
    cin >> n;
    string a, b;
    cin >> a >> b;

    vector<pair<int, int>> h_a, h_b;
    init_pow();
    build_hash(a, h_a);
    build_hash(b, h_b);

    int l = 0, r = n + 1;
    vector<pair<int, int>> segs;
    int ans_pos;
    while (r - l > 1) {
        int mid = (r + l) / 2;

        segs.clear();
        for (int i = 0; i + mid <= n; ++i) {
            segs.emplace_back(get_hash(h_a, i, mid, n));
        }

        int pos = -1;
        sort(segs.begin(), segs.end());
        for (int i = 0; i + mid <= n; ++i) {
            if (binary_search(segs.begin(), segs.end(), get_hash(h_b, i, mid, n))) {
                pos = i;
                break;
            }
        }

        if (pos >= 0) {
            l = mid;
            ans_pos = pos;
        } else {
            r = mid;
        }
    }
    cout << b.substr(ans_pos, l) << '\n';
}