#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
using ll = long long;
constexpr int INF = 0x3f3f3f3f;
constexpr ll LINF = 0x3f3f3f3f3f3f3f3fLL;
constexpr double EPS = 1e-8;
constexpr int MOD = 1000000007;
// constexpr int MOD = 998244353;
constexpr int dy[] = {1, 0, -1, 0}, dx[] = {0, -1, 0, 1};
constexpr int dy8[] = {1, 1, 0, -1, -1, -1, 0, 1}, dx8[] = {0, -1, -1, -1, 0, 1, 1, 1};
template <typename T, typename U> inline bool chmax(T &a, U b) { return a < b ? (a = b, true) : false; }
template <typename T, typename U> inline bool chmin(T &a, U b) { return a > b ? (a = b, true) : false; }
struct IOSetup {
  IOSetup() {
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    cout << fixed << setprecision(20);
  }
} iosetup;

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 a(n, vector(n, 0));
  REP(i, n) {
    if (s[i] == 2) {
      REP(j, n) a[i][j] = 1;
    }
  }
  REP(j, n) {
    if (t[j] == 2) {
      REP(i, n) a[i][j] = 1;
    }
  }
  int s1 = 0, t1 = 0;
  REP(i, n) {
    if (s[i] == 1) {
      int o = 0;
      REP(j, n) o |= a[i][j];
      s1 += o == 0;
    }
  }
  REP(j, n) {
    if (t[j] == 1) {
      int o = 0;
      REP(i, n) o |= a[i][j];
      t1 += o == 0;
    }
  }
  int ans = 0;
  REP(i, n) ans += count(ALL(a[i]), 1);
  cout << ans + max(s1, t1) << '\n';
  return 0;
}