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

int main(){
  int n;
  cin >> n;
  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;
    if(s[i] == 2) rep(j,n) a[i][j] = 1; 
    if(t[i] == 0) rep(j,n) a[j][i] = 0;
    if(t[i] == 2) rep(j,n) a[j][i] = 1;
  }
  rep(i,n) {
    if(s[i] == 1) {
      bool f = false;
      rep(j,n) if(a[i][j] == 1) f = true;
      if(f) rep(j,n) if(a[i][j] == -1) a[i][j] = 0;
    }
    if(t[i] == 1) {
      bool f = false;
      rep(j,n) if(a[j][i] == 1) f = true;
      if(f) rep(j,n) if(a[j][i] == -1) a[j][i] = 0;
    }
  }  
  int c = 0, r = 0;
  rep(i,n) {
    if(s[i] == 1) {
      bool f = false;
      rep(j,n) if(a[i][j] == 1) f = true;
      if(!f) c++; 
    }
    if(t[i] == 1) {
      bool f = false;
      rep(j,n) if(a[j][i] == 1) f = true;
      if(!f) r++;
    }
  }
  int ans = 0;
  rep(i,n) rep(j,n) if(a[i][j] == 1) ans++;
  cout << ans + max(r,c) << endl;
  return 0;
}