// Arup Guha
// 2/11/2017
// No Cross - Solution to both 2017 Feb USACO Gold and Platinum Problems: Why did the Cow Cross the Road II?

import java.util.*;
import java.io.*;

public class nocross {

	public static void main(String[] args) throws Exception {

		// Open file.
		BufferedReader stdin = new BufferedReader(new FileReader("nocross.in"));
		int n = Integer.parseInt(stdin.readLine().trim());

		// Get input.
		int[] f1 = new int[n];
		for (int i=0; i<n; i++)
			f1[i] = Integer.parseInt(stdin.readLine());

		int[] map = new int[n];

		// Store these in reverse.
		for (int i=0; i<n; i++)
			map[f1[i]-1] = i+1;

		// Get second input.
		int[] f2 = new int[n];
		for (int i=0; i<n; i++)
			f2[i] = Integer.parseInt(stdin.readLine());

		// minI[i] will store the minimum index from the bottom we link to the top to get i crosswalks.
		int[] minI = new int[n+1];
		Arrays.fill(minI, n+1);
		minI[0] = -1;
		int finalans = 0;

		// Go through each item.
		for (int i=0; i<n; i++) {

			// For f2[i], I want to find the list of items it can cross to.
			int low = Math.max(f2[i] - 5, 0);
			int high = Math.min(f2[i] + 3, n-1);
			int[] tmp = new int[high-low+1];

			// Basically, for where I am at, I can get to cows low through high, inclusive.
			// So I am trying each of these crosswalks.
			for (int j=low; j<=high; j++) {

				// This tells me the best answer if I were to link the cow at index i on the bottom to this
				// particular cow on the top.
				int res = binSearch(minI, map[j]) + 1;

				// Just storing all answers for doing a cross walk with cow in index i on the bottom.
				tmp[j-low] = res;
				finalans = Math.max(finalans, res);
			}

			// Now, this list has to be updated based on tmp, if we got a better answer than before for
			// any number of cross walks by adding one of these.
			for (int j=low; j<=high; j++) {
				minI[tmp[j-low]] = Math.min(minI[tmp[j-low]], map[j]);
			}

		}

		// Ta da!
		PrintWriter out = new PrintWriter(new FileWriter("nocross.out"));
		out.println(finalans);
		out.close();
		stdin.close();
	}

	// Finds largest i such that minI[i] < index.
	public static int binSearch(int[] minI, int index) {

		int low = 0, high = minI.length-1;
		while (low < high) {
			int mid = (low+high+1)/2;
			if (minI[mid] < index)
				low = mid;
			else
				high = mid-1;
		}
		return low;
	}
}