#include<bits/stdc++.h>
#define int long long
using namespace std;
const int N = 3e5 + 5;
constexpr int base = 173, mod = 1e9 + 7;
int n, ans;
char s[2][N];
int p0[N], p1[N], pw[N], t0[N], t1[N];
int len00[N], len01[N], len10[N], len11[N];
int check0(int l, int r, int now, bool opt/*奇偶*/) {
	while (l <= r) {
		int mid = l + r >> 1;
//		cout << "qwq0 " << (p0[now] - p0[now - mid] * pw[mid] % mod + mod) % mod << ' ' << (t0[now + opt] - t0[now + mid + opt] * pw[mid] % mod + mod) % mod << '\n';
		if ((p0[now] - p0[now - mid] * pw[mid] % mod + mod) % mod
		        == (t0[now + opt] - t0[now + mid + opt] * pw[mid] % mod + mod) % mod)
			l = mid + 1;
		else r = mid - 1;
	}
//	cout << l << '\n';
	return l - 1;
}
int check1(int l, int r, int now, bool opt/*奇偶*/) {
	while (l <= r) {
//		cout << "qwq1 " << l << '\n';
		int mid = l + r >> 1;
		if ((p1[now] - p1[now - mid] * pw[mid] % mod + mod) % mod
		        == (t1[now + opt] - t1[now + mid + opt] * pw[mid] % mod + mod) % mod)
			l = mid + 1;
		else r = mid - 1;
	}
	return l - 1;
}
int check(int l, int r, int nowl, int nowr) {
	while (l <= r) {
		//		cout << "qwq1 " << l << '\n';
		int mid = l + r >> 1;
		if ((p0[nowl] - p0[nowl - mid] * pw[mid] % mod + mod) % mod
		        == (t1[nowr] - t1[nowr + mid] * pw[mid] % mod + mod) % mod)
			l = mid + 1;
		else r = mid - 1;
	}
	return l - 1;
}
void Solve() {
	cin >> n, pw[0] = 1;
	for (int i = 1; i <= n; i ++) {
		cin >> s[0][i];
		p0[i] = p0[i - 1] * base + s[0][i];
		p0[i] %= mod;
		pw[i] = pw[i - 1] * base % mod;
	}
	for (int i = 1; i <= n; i ++) {
		cin >> s[1][i];
		p1[i] = p1[i - 1] * base + s[1][i];
		p1[i] %= mod;
	}
	for (int i = n; i; i --) {
		t0[i] = t0[i + 1] * base + s[0][i];
		t0[i] %= mod;
		t1[i] = t1[i + 1] * base + s[1][i];
		t1[i] %= mod;
	}
//	for(int i = n; i; i --) {
//
//	}
	for (int i = 1; i <= n; i ++) {
		len00[i] = check0(1, min(i, n - i + 1), i, 0);
		len01[i] = check0(1, min(i, n - i + 1), i, 1);
		ans = max({ans, len00[i] * 2 - 1, len01[i] * 2});
	}
	for (int i = 1; i <= n; i ++) {
		len10[i] = check1(1, min(i, n - i + 1), i, 0);
		len11[i] = check1(1, min(i, n - i + 1), i, 1);
		ans = max({ans, len10[i] * 2 - 1, len11[i] * 2});
	}
	for (int i = 1; i <= n; i ++) {
//		cout << p1[i] << ' ' << p0[i] << '\n';
//		cout << len00[i] << ' ' << len01[i] << ' ' << len10[i] << ' ' << len11[i] << '\n';
	}
	for (int i = 1; i <= n; i ++) {
		if(s[0][i] == s[1][i]) {
			ans = max(ans, check(0, min(i, n - i + 1), i, i) * 2);
		}
		ans = max(ans, len00[i] * 2 - 1 + check(0, n - len00[i] + 1 - i + 1, i - len00[i], i + len00[i] - 1) * 2);
//		if(ans == 8) cout << i << " 1\n";
		if(len01[i]) ans = max(ans, len01[i] * 2 + check(0, n - len01[i] - i + 1, i - len01[i], i + len01[i]) * 2);
//		if(ans == 8) cout << i << " 2\n";
		ans = max(ans, len10[i] * 2 - 1 + check(0, n - len10[i] - i + 1, i - len10[i] + 1, i + len10[i]) * 2);
//		if(ans == 8) cout << i << " 3\n";
		if(len11[i]) ans = max(ans, len11[i] * 2 + check(0, n - len11[i] - i + 2, i - len11[i] + 1, i + len11[i] + 1) * 2);
//		if(ans == 8) cout << i << " 4\n";
		
	}
	cout << ans << '\n';
}
signed main() {
	ios::sync_with_stdio(0);
	cin.tie(0), cout.tie(0);
	int T = 1;
//	cin >> T;
	while (T --) {
		Solve();
	}
	return 0;
}