#include<bits/stdc++.h>
using namespace std;

#define int long long
mt19937 gen(chrono::system_clock::now().time_since_epoch().count());
const int mod = (int)1e16 + gen(), base = gen() % 100 + 100;

vector<int> b{ 1 };
struct Hash {
	vector<int> h{ 0 };
	void append(auto& s) {
		for (auto x : s)
			h.push_back((h.back() * base + x) % mod);
		for (int i = b.size(); i <= s.size(); i++)
			b.push_back((b.back() * base) % mod);
	}
	int query(int l, int r) {
		if (l > r || l < 1 || r >= h.size())
			return gen();
		int x = h[r] - (__int128)h[l - 1] * b[r - l + 1] % mod;
		return x + (x < 0) * mod;
	}
	Hash() {}
	Hash(auto& s) {
		append(s);
	}
};

#define endl '\n'
using ll = long long;

void solve()
{
	int n;
	cin >> n;

	string s[2], t[2];
	cin >> t[0] >> t[1];
	s[0] = " " + t[0] + " ";
	s[1] = "  " + t[1];

	Hash h[2];
	h[0] = Hash(t[0]);
	string ht = " " + t[1];
	h[1] = Hash(ht);

	auto check = [&](auto p) {
		auto [x, y] = p;
		if (!x && (!y || y > n))
			return 0;
		if (x && (!y || y > n + 1))
			return 0;
		return 1;
	};
	auto lcp = [&](auto a, auto b) {
		auto [x1, y1] = a;
		auto [x2, y2] = b;
		if (!check(a) || !check(b) || s[x1][y1] != s[x2][y2])
			return 0ll;
		int l = 1, r = n;
		while (l < r) {
			int mid = (l + r + 1) / 2;
			if (h[x1].query(y1, y1 + mid - 1) == h[x2].query(y2, y2 + mid - 1))
				l = mid;
			else
				r = mid - 1;
		}
		return l;
	};
	auto lcs = [&](auto a, auto b) {
		auto [x1, y1] = a;
		auto [x2, y2] = b;
		if (!check(a) || !check(b) || s[x1][y1] != s[x2][y2])
			return 0ll;
		int l = 1, r = n;
		while (l < r) {
			int mid = (l + r + 1) / 2;
			if (h[x1].query(y1 - mid + 1, y1) == h[x2].query(y2 - mid + 1, y2))
				l = mid;
			else
				r = mid - 1;
		}
		return l;
	};

	int ans1 = 0, ans2 = 0, ans3 = 0;
	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= n; j += i) {
			int l = j, r = l + i - 1;
			// case1 : 
			if (r <= n) {

				int len1 = lcp(make_pair(0, l), make_pair(0, r + 1));
				int len2 = lcp(make_pair(0, l + len1), make_pair(1, r + len1 + 1));
				int len3 = lcs(make_pair(0, l - 1), make_pair(0, r));
				if (len1 + len2 + len3 >= i) {
					ans1 = max(ans1, 2 * i);
					break;
				}
			}
			// case2 :
			if (r <= n + 1) {
				int len1 = lcp(make_pair(1, l), make_pair(1, r + 1));
				int len2 = lcs(make_pair(1, l - 1), make_pair(1, r));
				int len3 = lcs(make_pair(0, l - len2 - 1), make_pair(1, r - len2));

				//debug(i, j, l - len2 - 1, r - len2, len1, len2, len3, endl);
				if (len1 + len2 + len3 >= i) {
					ans2 = max(ans2, 2 * i);
					break;
				}
			}
			// case3:
			if (r <= n) {
				int len1 = lcp(make_pair(0, l), make_pair(1, r + 1));
				int len2 = lcs(make_pair(0, l - 1), make_pair(1, r));
				//int len3 = lcs(make_pair(1, l + len1 + 1), make_pair(1, r + len1 + 1));

				//debug(i, len1, len2, len3, endl);
				//debug(l, r, endl);

				if (len1 + len2 >= i) {
					ans3 = max(ans3, 2 * i);
					break;
				}
			}
		}
	}

	//debug(ans1, ans2, ans3, endl);
	cout << max({ ans1, ans2, ans3 }) << endl;
}

signed main()
{
	ios::sync_with_stdio(0);
	cin.tie(0); cout.tie(0);
	solve();
}