#include <bits/stdc++.h>
#define rep(i,n) for (int i = 0; i < (int)(n); i ++)
#define irep(i,n) for (int i = (int)(n) - 1;i >= 0;--i)
using namespace std;
using ll = long long;
using PL = pair<ll,ll>;
using P = pair<int,int>;
constexpr int INF = 1000000000;
constexpr long long HINF = 1000000000000000;
constexpr long long MOD = 1000000007;// = 998244353;
constexpr double EPS = 1e-4;
constexpr double PI = 3.14159265358979;

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

    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>> ans(N,vector<int>(N,-1));
    rep(i,N) {
        if (S[i] == 0) {
            rep(j,N) ans[i][j] = 0;
        }
        if (S[i] == 2) {
            rep(j,N) ans[i][j] = 1;
        }
        if (T[i] == 0) {
            rep(j,N) ans[j][i] = 0;
        }
        if (T[i] == 2) {
            rep(j,N) ans[j][i] = 1;
        }
    }
    int r = 0,c = 0;
    rep(i,N) {
        if (S[i] == 1) {
            int cnt = 0;
            rep(j,N) if (ans[i][j] == 1) ++cnt;
            if (cnt == 0) ++r;
        }
        if (T[i] == 1) {
            int cnt = 0;
            rep(j,N) if (ans[j][i] == 1) ++cnt;
            if (cnt == 0) ++c;
        }
    }
    int A = max(r,c);
    rep(i,N) rep(j,N) if (ans[i][j] == 1) ++A;
    cout << A << '\n';
    return 0;
}