#ifndef LOCAL
#include <bits/stdc++.h>

using namespace std;

#define debug(...) (void(0))
#else
#include "algo/debug.h"
#endif

void solve() {
    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>> ans(N, vector<int>(N, 0));
    for (int i = 0; i < N; i++) {
        if (S[i] == 2)
            for (int j = 0; j < N; j++) ans[i][j] = 1;
        if (T[i] == 2)
            for (int j = 0; j < N; j++) ans[j][i] = 1;
    }
    vector<vector<int>> count(N, vector<int>(N));
    for (int i = 0; i < N; i++)
        if (S[i] == 1) {
            bool f = false;
            for (int j = 0; j < N; j++) {
                if (ans[i][j] == 1) f = true;
            }
            if (!f) {
                for (int j = 0; j < N; j++) count[i][j]++;
            }
        }
    for (int i = 0; i < N; i++)
        if (T[i] == 1) {
            bool f = false;
            for (int j = 0; j < N; j++) {
                if (ans[j][i] == 1) f = true;
            }
            if (!f) {
                for (int j = 0; j < N; j++) count[j][i]++;
            }
        }
    const auto Dec = [&](int i, int j) -> void {
        for (int k = 0; k < N; k++) count[i][k]--;
        for (int k = 0; k < N; k++) count[k][j]--;
    };
    for (int z : {2, 1}) {
        for (int i = 0; i < N; i++) {
            for (int j = 0; j < N; j++) {
                if (count[i][j] == z) {
                    ans[i][j] = 1;
                    Dec(i, j);
                }
            }
        }
    }
    debug(ans);
    int sum = 0;
    for (int i = 0; i < N; i++) {
        for (int j = 0; j < N; j++) {
            sum += ans[i][j];
        }
    }
    cout << sum << endl;
}

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    int tt = 1;
    // std::cin >> tt;
    while (tt--) {
        solve();
    }
}