#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<(int)(n); i++)

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  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> > a(n, vector<int>(n, -1));

  REP (i, n) {
    if (s[i] == 0) {
      REP (j, n) a[i][j] = 0;
    } else if (s[i] == 2) {
      REP (j, n) a[i][j] = 1;
    }
  }

  REP (i, n) {
    if (t[i] == 0) {
      REP (j, n) a[j][i] = 0;
    } else if (t[i] == 2) {
      REP (j, n) a[j][i] = 1;
    }
  }

  int r = 0, c = 0;
  REP (i, n) {
    if (s[i] == 1) {
      int z = 0;
      REP (j, n) z += a[i][j] == 1;
      if (z == 0)
        ++r;
    }
  }

  REP (i, n) {
    if (t[i] == 1) {
      int z = 0;
      REP (j, n) z += a[j][i] == 1;
      if (z == 0)
        ++c;
    }
  }

  int ret = max(r, c);
  REP (i, n) REP (j, n) if (a[i][j] == 1) ++ret;

  cout << ret << endl;
  
  return 0;
}