#include<bits/stdc++.h>
#define eb emplace_back
#define ep emplace
using namespace std;

using ll = long long;
constexpr int N = 1e5 + 5, P = 1e9 + 7;

int n, ans; char s[N], t[N];
ll pw[N] = {1};

struct H {
	ll h[N], g[N];	
	void init(int n, char* s) {
		for(int i = 1; i <= n; ++ i) h[i] = (h[i - 1] * 131 + s[i]) % P;
		for(int i = n; i >= 1; -- i) g[i] = (g[i + 1] * 131 + s[i]) % P;
	}
	ll get(int l, int r) {
		return (h[r] + P - h[l - 1] * pw[r - l + 1] % P) % P;
	}
	ll rev(int l, int r) {
		return (g[l] + P - g[r + 1] * pw[r - l + 1] % P) % P;
	}
} h[2];

auto R(int p, int i, int o) {
	int l = 1, r = min(p, n - p + o);
	while(l < r) {
		int mid = l + r + 1 >> 1;
		h[i].get(p + !o, p + mid - o) == h[i].rev(p - mid + 1, p) ? l = mid : r = mid - 1;
	}
	return make_pair(p - l + 1, p + l - o);
}
int L(int i, int j) {
	if(s[i] != t[j]) return 0;
	int l = 1, r = min(i, n - j + 1);
	while(l < r) {
		int mid = l + r + 1 >> 1;
		h[0].rev(i - mid + 1, i) == h[1].get(j, j + mid - 1) ? l = mid : r = mid - 1;
	}
	return l;
}
int main() {
	scanf("%d%s%s", &n, s + 1, t + 1);
	h[0].init(n, s);
	h[1].init(n, t);
	for(int i = 1; i <= n; ++ i) pw[i] = pw[i - 1] * 131 % P;
	for(int i = 1; i <= n; ++ i) {
		auto [l, r] = R(i, 0, 1);
		ans = max(ans, r - l + 1 + 2 * L(l - 1, r));
		if(l == i) {
			ans = max(ans, 2 * L(i, i));
		}
		if(s[i] == s[i + 1]) {
			auto[l, r] = R(i, 0, 0);
			ans = max(ans, r - l + 1 + 2 * L(l - 1, r));
		}
	}
	for(int i = 1; i <= n; ++ i) {
		auto [l, r] = R(i, 1, 1);		
		ans = max(ans, r - l + 1 + 2 * L(l, r + 1));
		if(t[i] == t[i + 1]) {
			auto[l, r] = R(i, 1, 0);
			ans = max(ans, r - l + 1 + 2 * L(l, r + 1));
		}
	}
	cout << ans;
	return 0;
}