// Template
#include <bits/stdc++.h>
#define rep_override(x, y, z, name, ...) name
#define rep2(i, n) for (int i = 0; i < (int)(n); ++i)
#define rep3(i, l, r) for (int i = (int)(l); i < (int)(r); ++i)
#define rep(...) rep_override(__VA_ARGS__, rep3, rep2)(__VA_ARGS__)
#define per(i, n) for (int i = (int)(n) - 1; i >= 0; --i)
#define all(x) (x).begin(), (x).end()
using namespace std;
using ll = long long;
constexpr int inf = 1001001001;
constexpr ll INF = 3003003003003003003LL;
template <typename T> inline bool chmin(T &x, const T &y) {if (x > y) {x = y; return 1;} return 0;}
template <typename T> inline bool chmax(T &x, const T &y) {if (x < y) {x = y; return 1;} return 0;}
struct IOSET {IOSET() {cin.tie(0); ios::sync_with_stdio(0); cout << fixed << setprecision(10);}} ioset;

// Main
int main() {
    int n;
    cin >> n;
    vector<int> s(n), t(n);
    rep(i, n) cin >> s[i];
    rep(i, n) cin >> t[i];
    
    vector<vector<int>> a(n, vector<int>(n, 0));
    rep(i, n) {
        if (s[i] == 2) {
            rep(j, n) a[i][j] = 1;
        }
        if (t[i] == 2) {
            rep(j, n) a[j][i] = 1;
        }
    }
    
    int cnt0 = 0, cnt1 = 0, sum = 0;
    rep(i, n) {
        if (s[i] == 0 || s[i] == 2) continue;
        bool f = true;
        rep(j, n) {
            if (a[i][j]) f = false;
        }
        if (f) ++cnt0;
    }
    rep(i, n) {
        if (t[i] == 0 || t[i] == 2) continue;
        bool f = true;
        rep(j, n) {
            if (a[j][i]) f = false;
        }
        if (f) ++cnt1;
    }
    rep(i, n) rep(j, n) sum += a[i][j];
    
    cout << max(cnt0, cnt1) + sum << "\n";
}