#include <iostream>
#include <numeric>
#include <vector>

template <class T>
std::vector<T> vec(int len, T elem) { return std::vector<T>(len, elem); }

void solve() {
    int n;
    std::cin >> n;

    auto grid = vec(n, vec(n, 0));

    std::vector<int> xs(n);
    for (int i = 0; i < n; ++i) {
        auto& x = xs[i];

        std::cin >> x;
        if (x == 2) {
            for (int j = 0; j < n; ++j) grid[i][j] = 1;
        }
    }

    std::vector<int> ys(n);
    for (int j = 0; j < n; ++j) {
        auto& y = ys[j];

        std::cin >> y;
        if (y == 2) {
            for (int i = 0; i < n; ++i) grid[i][j] = 1;
        }
    }

    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < n; ++j) {
            if (grid[i][j] == 1) {
                xs[i] = 0;
                ys[j] = 0;
            }
        }
    }

    int ans = std::max(std::accumulate(xs.begin(), xs.end(), 0),
                       std::accumulate(ys.begin(), ys.end(), 0));

    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < n; ++j) {
            ans += grid[i][j];
        }
    }

    std::cout << ans << "\n";
}

int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    solve();

    return 0;
}