#include <bits/stdc++.h>
#define rep(a,n) for (ll a = 0; a < (n); ++a)
using namespace std;
//using namespace atcoder;
using ll = long long;
typedef pair<ll,ll> P;
typedef pair<ll,P> PP;
typedef vector<vector<int> > Graph;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
const ll INF = 1e18;

int now[510][510];

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    //input
    ll n;
    cin >> n;
    vector<int>s(n),t(n);
    rep(i,n)cin>>s[i];
    rep(i,n)cin>>t[i];

    rep(i,n)rep(j,n)now[i][j]=-1;

    vector<bool>tate(n,false),yoko(n,false);//確定したか
    rep(i,n){
        if(s[i]==0){
            tate[i]=true;
            rep(j,n){
                now[i][j]=0;
            }
        }
        if(s[i]==2){
            tate[i]=true;
            rep(j,n){
                now[i][j]=1;
            }
        }
        if(t[i]==0){
            yoko[i]=true;
            rep(j,n){
                now[j][i]=0;
            }
        }
        if(t[i]==2){
            yoko[i]=true;
            rep(j,n){
                now[j][i]=1;
            }
        }
    }

    rep(i,n){
        if(s[i]==1){
            bool flag = false;
            rep(j,n){
                if(now[i][j]==1){
                    flag=true;
                }
            }
            if(flag){
                tate[i]=true;
                rep(j,n){
                    if(now[i][j]==-1){
                        now[i][j]=0;
                    }
                }
            }
        }
        if(t[i]==1){
            bool flag = false;
            rep(j,n){
                if(now[j][i]==1){
                    flag=true;
                }
            }
            if(flag){
                yoko[i]=true;
                rep(j,n){
                    if(now[j][i]==-1){
                        now[j][i]=0;
                    }
                }
            }
        }
    }

    ll cnt_tate = 0;
    ll cnt_yoko = 0;
    rep(i,n){
        if(!tate[i]){
            cnt_tate++;
        }
        if(!yoko[i]){
            cnt_yoko++;
        }
    }
    ll cnt = 0;
    rep(i,n)rep(j,n)if(now[i][j]==1)cnt++;
    cout << cnt + max(cnt_tate,cnt_yoko) << endl;

    return 0;
}