#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(int)n;i++)
using namespace std;
using ll = long long;
using P = pair<int, int>;

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>> ans(n, vector<int>(n, 0));
    rep(i,n) {
        if (s[i] == 2) {
            rep(j,n) {
                ans[i][j] = 1;
            }
        }
    }
    rep(i,n) {
        if (t[i] == 2) {
            rep(j,n) {
                ans[j][i] = 1;
            }
        }
    }
    int a = 0, b = 0;
    rep(i,n) {
        if (s[i] == 1) {
            bool find = false;
            rep(j,n) {
                if (ans[i][j]) find = true;
            }
            if (!find) a++;
        }
        if (t[i] == 1) {
            bool find = false;
            rep(j,n) {
                if (ans[j][i]) find = true;
            }
            if (!find) b++;
        }
    }
    int sum = 0;
    rep(i,n) {
        rep(j,n) {
            sum += ans[i][j];
        }
    }
    cout << sum + max(a, b) << endl;
    return 0;
}