#include <iostream>
#include <string>
#include <cstdlib>
#include <cmath>
#include <vector>
#include <unordered_map>
#include <map>
#include <set>
#include <algorithm>
#include <queue>
#include <stack>
#include <functional>
#include <bitset>
#include <assert.h>
#include <unordered_map>
#include <fstream>
#include <ctime>
#include <complex>
using namespace std;
typedef long long ll;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<char> vc;
typedef vector<string> vs;
typedef vector<bool> vb;
typedef vector<double> vd;
typedef pair<ll,ll> P;
typedef pair<int,int> pii;
typedef vector<P> vpl;
typedef tuple<ll,ll,ll> tapu;
#define rep(i,n) for(int i=0; i<(n); i++)
#define REP(i,a,b) for(int i=(a); i<(b); i++)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
const int inf = 1<<30;
const ll linf = 1LL<<62;
const int MAX = 510000;
ll dy[8] = {1,-1,0,0,1,-1,1,-1};
ll dx[8] = {0,0,1,-1,1,-1,-1,1};
const double pi = acos(-1);
const double eps = 1e-7;
template<typename T1,typename T2> inline bool chmin(T1 &a,T2 b){
	if(a>b){
		a = b; return true;
	}
	else return false;
}
template<typename T1,typename T2> inline bool chmax(T1 &a,T2 b){
	if(a<b){
		a = b; return true;
	}
	else return false;
}
template<typename T> inline void print(T &a){
    rep(i,a.size()) cout << a[i] << " ";
    cout << "\n";
}
template<typename T1,typename T2> inline void print2(T1 a, T2 b){cout << a << " " << b << "\n";}
template<typename T1,typename T2,typename T3> inline void print3(T1 a, T2 b, T3 c){
	cout << a << " " << b << " " << c << "\n";
}
ll pcount(ll x) {return __builtin_popcountll(x);}
const int mod = 1e9 + 7;
//const int mod = 998244353;

int a[505][505];

int main(){
    int n; cin >> n;
    vl s(n), t(n);
    rep(i,n) cin >> s[i];
    rep(j,n) cin >> t[j];
    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;
        }
    }
    vb v(n,false);
    rep(i,n){
        if(s[i] == 1){
            bool f = false;
            rep(j,n){
                if(a[i][j] == 1) f = true;
            }
            if(f) continue;
            rep(j,n){
                if(t[j] == 1 && !v[j]){
                    a[i][j] = 1;
                    v[j] = true;
                    f = true;
                    break;
                } 
            }
            if(f) continue;
            rep(j,n){
                if(t[j]){
                    a[i][j] = 1;
                    break;
                }
            }
        }
    }
    rep(j,n){
        if(t[j] == 0 || t[j] == 2 || v[j]) continue;
        bool f = false;
        rep(i,n){
            if(a[i][j] == 1){
                f = true;
                break;
            }
        }
        if(f) continue;
        rep(i,n){
            if(s[i]){
                a[i][j] = 1;
                break;
            }
        }
    }
    int ans = 0;
    rep(i,n) rep(j,n) ans += a[i][j];
    cout << ans << "\n";
}