#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <queue>
#include <string>
#include <map>
#include <set>
#include <stack>
#include <tuple>
#include <deque>
#include <array>
#include <numeric>
#include <bitset>
#include <iomanip>
#include <cassert>
#include <chrono>
#include <random>
#include <limits>
#include <iterator>
#include <functional>
#include <sstream>
#include <fstream>
#include <complex>
#include <cstring>
#include <unordered_map>
#include <unordered_set>
using namespace std;

using ll = long long;
using P = pair<int, int>;
constexpr int INF = 1001001001;
// constexpr int mod = 1000000007;
constexpr int mod = 998244353;

template<class T>
inline bool chmax(T& x, T y){
    if(x < y){
        x = y;
        return true;
    }
    return false;
}
template<class T>
inline bool chmin(T& x, T y){
    if(x > y){
        x = y;
        return true;
    }
    return false;
}

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

    int n;
    cin >> n;
    vector<int> s(n), t(n);
    vector<vector<int>> a(n, vector<int>(n));
    vector<bool> fs(n), ft(n);
    set<int> ones, onet;
    for(int i = 0; i < n; ++i){
        cin >> s[i];
        if(s[i] == 2){
            for(int j = 0; j < n; ++j){
                a[i][j] = 1;
                ft[j] = true;
            }
        }
    }
    for(int j = 0; j < n; ++j){
        cin >> t[j];
        if(t[j] == 2){
            for(int i = 0; i < n; ++i){
                a[i][j] = 1;
                fs[i] = true;
            }
        }
    }

    for(int i = 0; i < n; ++i){
        if(s[i] == 0 || s[i] == 2 || fs[i]) continue;
        ones.emplace(i);
    }
    for(int j = 0; j < n; ++j){
        if(t[j] == 0 || t[j] == 2 || ft[j]) continue;
        onet.emplace(j);
    }

    int ans = 0;
    for(int i = 0; i < n; ++i){
        for(int j = 0; j < n; ++j){
            ans += a[i][j];
        }
    }
    ans += max(ones.size(), onet.size());

    cout << ans << endl;

    return 0;
}