#include <bits/stdc++.h>
using namespace std;
#define REP(i, n) for (int i = 0; i < (int)(n); i++)
typedef long long ll;
typedef pair<int, int> P;
const int INF = 1e9;
const ll MOD = 1000000007;
int main() {
  ll N;
  cin >> N;
  vector<int> S(N), T(N);
  REP(i, N) cin >> S[i];
  REP(i, N) cin >> T[i];
  vector<vector<int>> Vec(N, vector<int>(N, 0));
  REP(i, N) {
    if (S[i] == 2) {
      REP(j, N) Vec[i][j] = 1;
    }
    if (T[i] == 2) {
      REP(j, N) Vec[j][i] = 1;
    }
  }
  int _s = 0, _t = 0;
  REP(i, N) {
    if (S[i] == 1) {
      bool b = false;
      REP(j, N) if (Vec[i][j] == 1) b = true;
      if (!b) _s++;
    }
    if (T[i] == 1) {
      bool b = false;
      REP(j, N) if (Vec[j][i] == 1) b = true;
      if (!b) _t++;
    }
  }
  int sum = 0;
  REP(i, N) REP(j, N) if (Vec[i][j] == 1) sum++;
  cout << sum + max(_s, _t) << endl;
}