#include <cstdio>

#include <iostream>

#include <algorithm>

#define N 100001

#define root 1, 1, n

#define ls now << 1, l, mid

#define rs now << 1 | 1, mid + 1, r

using namespace std;

int n, ans, cnt;

int a[N], pos[N], sum[N << 2], f[N];

inline int read()

{

	int x = 0, f = 1;

	char ch = getchar();

	for(; !isdigit(ch); ch = getchar()) if(ch == '-') f = -1;

	for(; isdigit(ch); ch = getchar()) x = (x << 1) + (x << 3) + ch - '0';

	return x * f;

}

inline int query(int now, int l, int r, int x, int y)

{

	if(x > y) return 0;

	if(x <= l && r <= y) return sum[now];

	int mid = (l + r) >> 1, ret = 0;

	if(x <= mid) ret = max(ret, query(ls, x, y));

	if(mid < y) ret = max(ret, query(rs, x, y));

	return ret;

}

inline void update(int now, int l, int r, int x, int d)

{

	if(l == r)

	{

		sum[now] = max(sum[now], d);

		return;

	}

	int mid = (l + r) >> 1;

	if(x <= mid) update(ls, x, d);

	else update(rs, x, d);

	sum[now] = max(sum[now << 1], sum[now << 1 | 1]);

}

int main()

{

	int i, j, x;

	n = read();

	for(i = 1; i <= n; i++) x = read(), pos[x] = i;

	for(i = 1; i <= n; i++)

	{

		cnt = 0;

		x = read();

		for(j = max(1, x - 4); j <= min(n, x + 4); j++) a[++cnt] = pos[j];

		sort(a + 1, a + cnt + 1);

		for(j = cnt; j >= 1; j--)

		{

			x = query(root, 1, a[j] - 1) + 1;

			f[a[j]] = max(f[a[j]], x);

			update(root, a[j], x);

		}

	}

	for(i = 1; i <= n; i++) ans = max(ans, f[i]);

	printf("%d\n", ans);

	return 0;

}