#include <bits/stdc++.h>
using namespace std;
// #include <atcoder/all>
// using namespace atcoder;

typedef long long ll;
typedef pair<ll,ll> P;
typedef pair<P,ll> PLL;
typedef pair<P,P> PP;
typedef vector<ll> llVEC;
typedef vector<P> PVEC;
typedef priority_queue<P,PVEC,greater<P> > PPQ;
typedef priority_queue<ll, llVEC, greater<ll> > llPQ;

#define rep(i,a,n) for(ll i = a;i < n;i++)
#define rrep(i,a,n) for(ll i = n-1; i >= a;i--)
#define index_check(i,n) if(i > n-1 || i < 0) continue;
#define LINF (ll)1e18
#define INF (int)1e9
#define fs first
#define sc second

template<typename T>
ll sz(vector<T> &vec){ return (ll)vec.size(); }
ll sz(string &s){ return (ll)s.size(); }
ll gcd(ll a,ll b){ return ((!b) ?a :gcd(b, a%b)); }
ll lcm(ll a,ll b){ return a / gcd(a,b) * b; }


int main(){
    ll n,sum = 0;
    cin >> n;
    ll s[n],t[n] = {};
    rep(i,0,n) cin >> s[i];
    rep(i,0,n) cin >> t[i];
    ll a[n][n] = {};
    ll cnts[n] = {},cntt[n] = {};

    rep(i,0,n){
        rep(j,0,n){
            if(s[i] == 2 || t[j] == 2) a[i][j] = 1;
            sum += a[i][j];
            cnts[i] += a[i][j];
            cntt[j] += a[i][j];
        }
    }

    ll memos = 0,memot = 0;
    rep(i,0,n) if(s[i] == 1 && cnts[i] == 0) memos++;
    rep(i,0,n) if(t[i] == 1 && cntt[i] == 0) memot++;

    cout << sum + max(memos,memot) << endl;
    return 0;
}