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

#include <iostream>
#include <vector>

using namespace std;

int solve(vector<int> A, vector<int> B)
{
    int result = 1;
    int alen = 1, blen = 1, n = A.size();
    
    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 = max(a, blen + 1);
        }
        
        if (B[i] >= A[i - 1])
        {
            b = alen + 1;
        }
        
        if (B[i] >= B[i - 1])
        {
            b = max(b, blen + 1);
        }
        
        alen = a;
        blen = b;
        result = max(result, alen);
        result = max(result, blen);
    }
    
    return result;
}

int main()
{
    int size;
    cin >> size;
    
    vector<int> A(size);
    vector<int> B(size);
    
    for (int i = 0; i < size; i++)
    {
        cin >> A[i];
    }
    
    for (int i = 0; i < size; i++)
    {
        cin >> B[i];
    }
    
    cout << solve(A, B) << endl;
    
    return 0;
}