#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rrep(i, n) for (int i = (int)(n - 1); i >= 0; i--)
#define all(x) (x).begin(), (x).end()
#define sz(x) int(x.size())
using namespace std;
typedef long long ll;
const int INF = 1e9;
const ll MOD = 1e9 + 7;
const ll LINF = 1e18;
template <class T>
void get_unique(vector<T>& x) {
    x.erase(unique(x.begin(), x.end()), x.end());
}
template <class T>
bool chmax(T& a, const T& b) {
    if (a < b) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
bool chmin(T& a, const T& b) {
    if (b < a) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
vector<T> make_vec(size_t a) {
    return vector<T>(a);
}
template <class T, class... Ts>
auto make_vec(size_t a, Ts... ts) {
    return vector<decltype(make_vec<T>(ts...))>(a, make_vec<T>(ts...));
}
template <typename T>
ostream& operator<<(ostream& os, vector<T> v) {
    for (int i = 0; i < sz(v); i++) {
        os << v[i];
        if (i < sz(v) - 1) os << " ";
    }
    return os;
}
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));
    bool oks = 0, okt = 0;
    rep(i, n) {
        if (s[i] == 2) {
            rep(j, n) a[i][j] = 1;
            oks = 1;
        }
    }
    rep(j, n) {
        if (t[j] == 2) {
            rep(i, n) a[i][j] = 1;
            okt = 1;
        }
    }
    if (!okt && !oks) {
        cout << max(accumulate(all(s), 0), accumulate(all(t), 0)) << '\n';
        return 0;
    }
    rep(i, n) {
        if (s[i] == 1 && !okt) {
            rep(j, n) {
                if (a[i][j] == 0) {
                    a[i][j] = 1;
                    break;
                }
            }
        }
    }
    rep(j, n) {
        if (t[j] == 1 && !oks) {
            rep(i, n) {
                if (a[i][j] == 0) {
                    a[i][j] = 1;
                    break;
                }
            }
        }
    }
    int ans = 0;
    rep(i, n) rep(j, n) ans += a[i][j];
    cout << ans << '\n';
}