#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main() {
    int n;
    cin >> n;
    vector<int> s(n), t(n);
    for (int i = 0; i < n; i++)cin >> s[i];
    for (int i = 0; i < n; i++)cin >> t[i];

    vector<vector<int>> v(n, vector<int>(n, -1));
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            if (s[i] == 0 || t[j] == 0)v[i][j] = 0;
            else if (s[i] == 2 || t[j] == 2)v[i][j] = 1;
        }
    }

    int a = 0, b = 0;
    for (int i = 0; i < n; i++) {
        if (s[i] == 1) {
            bool found = false;
            for (int j = 0; j < n; j++) {
                if (v[i][j] == 1)found = true;
            }
            if (!found)a++;
        }
        if (t[i] == 1) {
            bool found = false;
            for (int j = 0; j < n; j++) {
                if (v[j][i] == 1)found = true;
            }
            if (!found)b++;
        }
    }

    int ret = 0;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            ret += max(0, v[i][j]);
        }
    }

    cout << ret + max(a, b) << endl;
    return 0;
}