// 2024 IUSB Programming Competition
// Round 2 Problem 3
// New Array
// Solution by Liguo Yu

import java.util.Scanner;

public class round2_p3
{
    public static void main(String[] args)
    {
        Scanner input = new Scanner(System.in);
        int size = input.nextInt();
        
        int[] A = new int[size];
        int[] B = new int[size];
        
        for(int i=0; i<size; i++)
        {
            A[i] = input.nextInt();
        }
        
        for(int i=0; i<size; i++)
        {
            B[i] = input.nextInt();
        }
        
        System.out.println(solve(A, B));
    }
    
    public static int solve(int[] A, int[] B)
    {
        int result = 1;
        int alen = 1, blen = 1, n = A.length;
        
        if (n<1)
        {
            return 0;
        }
        for (int i=1; i<n; ++i)
        {
            int a = 1, b = 1;

            if (A[i] >= A[i-1])
            {
                a = alen+1;
            }
            
            if (A[i] >= B[i-1])
            {
                a = Math.max(a, blen+1);
            }
            
            if (B[i] >= A[i-1])
            {
                b = alen+1;
            }
            
            if (B[i] >= B[i-1])
            {
                b = Math.max(b, blen+1);
            }
            
            alen = a;
            blen = b;
            result = Math.max(result,alen);
            result = Math.max(result,blen);
        }
        
        return result;
    }    
}