#include <bits/stdc++.h>
#define For(i, a, b) for (int(i) = (int)(a); (i) < (int)(b); ++(i))
#define rFor(i, a, b) for (int(i) = (int)(a)-1; (i) >= (int)(b); --(i))
#define rep(i, n) For((i), 0, (n))
#define rrep(i, n) rFor((i), (n), 0)
#define fi first
#define se second
using namespace std;
typedef long long lint;
typedef unsigned long long ulint;
typedef pair<int, int> pii;
typedef pair<lint, lint> pll;
template <class T>
bool chmax(T &a, const T &b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
template <class T>
bool chmin(T &a, const T &b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template <class T>
T div_floor(T a, T b) {
    if (b < 0) a *= -1, b *= -1;
    return a >= 0 ? a / b : (a + 1) / b - 1;
}
template <class T>
T div_ceil(T a, T b) {
    if (b < 0) a *= -1, b *= -1;
    return a > 0 ? (a - 1) / b + 1 : a / b;
}

constexpr lint mod = 1000000007;
constexpr lint INF = mod * mod;
constexpr int MAX = 200010;

int main() {
    int n;
    scanf("%d", &n);
    int a[n][n];
    rep(i, n) rep(j, n) a[i][j] = -1;
    int s[n], t[n];
    rep(i, n) {
        scanf("%d", &s[i]);
        if (s[i] == 0) rep(j, n) a[i][j] = 0;
        if (s[i] == 2) rep(j, n) a[i][j] = 1;
    }
    rep(j, n) {
        scanf("%d", &t[j]);
        if (t[j] == 0) rep(i, n) a[i][j] = 0;
        if (t[j] == 2) rep(i, n) a[i][j] = 1;
    }

    int ans = 0;
    rep(i, n) rep(j, n) ans += (a[i][j] == 1);
    int h = 0, w = 0;
    rep(i, n) if (s[i] == 1) {
        bool flag = false;
        rep(j, n) if (a[i][j] == 1) {
            flag = true;
            break;
        }
        if (!flag) ++h;
    }
    rep(j, n) if (t[j] == 1) {
        bool flag = false;
        rep(i, n) if (a[i][j] == 1) {
            flag = true;
            break;
        }
        if (!flag) ++w;
    }
    ans += max(h, w);
    printf("%d\n", ans);
}