#include <bits/stdc++.h>
#define int unsigned long long
using namespace std;
const int N = 2e5 + 5;
const int base = 37;
int n, h1[N], h2[N], p[N], pw[N];
char s[N], t[N];
int cal1(int l, int r) {
	return h1[l] - h1[r + 1] * pw[r - l + 1];
}
int cal2(int l, int r) {
	return h2[r] - h2[l - 1] * pw[r - l + 1];
}
int solve() {
	char a[N]; a[1] = '@'; int ts = 1; pw[0] = 1;
	for (int i = 1; i <= n; i++) {
		h2[i] = h2[i - 1] * base + t[i] - 'a' + 1;
		pw[i] = pw[i - 1] * base;
	}
	for (int i = n; i >= 1; i--)
		h1[i] = h1[i + 1] * base + s[i] - 'a' + 1;
	for (int i = 1; i <= n; i++)
		a[++ts] = '#', a[++ts] = s[i];
	a[++ts] = '#', a[++ts] = '$'; int ans = 0;
	for (int i = 1; i <= n; i++) {
		int l = 1, r = min(i, n - i + 1), len = 0;
		while (l <= r) {
			int mid = l + r >> 1;
			if (cal1(i - mid + 1, i) ==
				cal2(i, i + mid - 1)) len = mid, l = mid + 1;
			else r = mid - 1;
		}
		ans = max(ans, len * 2);
	}
	for (int i = 2, mid, R = 0; i < ts; i++) {
		p[i] = (R >= i ? min(p[mid * 2 - i], R - i + 1) : 1);
		while (a[i + p[i]] == a[i - p[i]]) p[i]++;
		if (i + p[i] - 1 > R) R = i + p[i] - 1, mid = i;
		if (a[i] == '#' && p[i] == 1) continue;
		int pos1 = (i - p[i] + 1) / 2, pos2 = (i + p[i] - 1) / 2 - 1;
		int l = 1, r = min(pos1 - 1, n - pos2 + 1), len = 0;
		while (l <= r) {
			int mid = l + r >> 1;
			if (cal1(pos1 - mid, pos1 - 1) ==
				cal2(pos2, pos2 + mid - 1)) len = mid, l = mid + 1;
			else r = mid - 1;
		}
		ans = max(ans, pos2 - pos1 + 1 + len * 2);
	}
	return ans;
}
signed main() {
	cin >> n >> s + 1 >> t + 1; int ans = solve();
	reverse(s + 1, s + 1 + n), reverse(t + 1, t + 1 + n); 
	swap(s, t), cout << max(ans, solve()) << '\n';
	return 0;
}