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

int main(){
    int n; cin>>n;
    int s[n+1],t[n+1];
    rep(i,n) cin>>s[i+1];
    rep(i,n) cin>>t[i+1];

    int a[n+1][n+1];
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            a[i][j] = -1;
        }
    }

    for(int i=1;i<=n;i++){
        if(s[i]==0){
            for(int j=1;j<=n;j++){
                a[i][j] = 0;
            }
        }else if(s[i]==2){
            for(int j=1;j<=n;j++){
                a[i][j] = 1;
            }
        }
    }

    for(int i=1;i<=n;i++){
        if(t[i]==0){
            for(int j=1;j<=n;j++){
                a[j][i] = 0;
            }
        }else if(t[i]==2){
            for(int j=1;j<=n;j++){
                a[j][i] = 1;
            }
        }
    }

    for(int i=1;i<=n;i++){
        if(s[i]==1){
            for(int j=1;j<=n;j++){
                if(t[j]==1){
                    a[i][j] = 1;
                    t[j] = -1;
                    break;
                }
            }
        }
    }

    int ans = 0;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            if(a[i][j]!=-1) ans += a[i][j];
        }
    }

    cout << ans << endl;
}