#include <bits/stdc++.h>
using namespace std;
const int N = 1e6 + 6;
int n, ps[N], pt[N], ans; char s[N], t[N];
int sa[N], rk[N], id[N], c[N], _rk[N], h[N], ST[N][20];
void getp(int n, char *s, int *p) {
	char t[N];
	for (int i=1; i<n<<1; i++)
		t[i] = i & 1 ? s[i+1>>1] : 0;
	for (int i=1, j=0; i<n<<1; i++) {
		if (i < j + p[j]) p[i] = min(p[(j<<1)-i], j + p[j] - i);
		while (i + p[i] < n << 1 && i - p[i] && t[i+p[i]] == t[i-p[i]]) p[i] ++;
		if (i + p[i] > j + p[j]) j = i;
	}
}
void geth(int n, char *s) {
	int m = 128;
	for (int i=1; i<=n; i++) sa[i] = i, rk[i] = s[i];
	for (int k=0; k<=n; k=k?k<<1:1) {
		int t = 0;
		for (int i=n-k+1; i<=n; i++) id[++t] = i;
		for (int i=1; i<=n; i++) if (sa[i] > k) id[++t] = sa[i] - k;
		for (int i=1; i<=m; i++) c[i] = 0;
		for (int i=1; i<=n; i++) c[rk[id[i]]] ++;
		for (int i=1; i<=m; i++) c[i] += c[i-1];
		for (int i=n; i; i--) sa[c[rk[id[i]]]--] = id[i];
		m = 0;
		for (int i=1; i<=n; i++) _rk[sa[i]] = rk[sa[i]] == rk[sa[i-1]] && rk[sa[i]+k] == rk[sa[i-1]+k] ? m : ++ m;
		for (int i=1; i<=n; i++) rk[i] = _rk[i];
		if (m == n) break;
	}
	for (int i=1, j=0; i<=n; i++) {
		if (j) j --;
		while (s[i+j] == s[sa[rk[i]-1]+j]) j ++;
		h[rk[i]] = j;
	}
	for (int i=1; i<=n; i++)
		ST[i][0] = h[i];
	for (int j=1; j<=__lg(n); j++)
		for (int i=1; i<=n; i++) {
			ST[i][j] = ST[i][j-1];
			if (i + (1 << j - 1) <= n)
				ST[i][j] = min(ST[i][j], ST[i+(1<<j-1)][j-1]);
		}
}
int qry(int l, int r) {
	l = rk[l], r = rk[r];
	if (l > r) swap(l, r);
	int k = __lg(r - l);
	return min(ST[l+1][k], ST[r-(1<<k)+1][k]);
}
int main() {
	scanf ("%d%s%s", &n, s+1, t+1);
	getp(n, s, ps), getp(n, t, pt);
	reverse (s+1, s+n+1), s[n+1] = ' ', t[n+1] = '!';
	for (int i=n+2; i<=n+1<<1; i++)
		s[i] = t[i-n-1];
	geth(n+1<<1, s);
	for (int i=1; i<n<<1; i++) {
		int l = i - ps[i] + 3 >> 1, r = i + ps[i] >> 1;
		ans = max(ans, r - l + 1 + (qry(n - l + 2, n + r + 1) << 1));
		l = i - pt[i] + 3 >> 1, r = i + pt[i] >> 1;
		ans = max(ans, r - l + 1 + (qry(n - l + 1, n + r + 2) << 1));
	} cout << ans;
}