#include <bits/stdc++.h>

#define INF 1e9
#define LINF (1LL << 63 - 1)
#define rep(i,n)for(int i=0;(i)<(int)(n);i++)
#define REP(i,a,b)for(int i=(int)(a);(i)<=(int)(b);i++)
#define ALL(a)  (a).begin(),(a).end()
// #define chmax(a, b) a = max(a, b)
// #define chmin(a, b) a = min(a, b)
#define pb push_back
#define fi first
#define se second
#define sz(x) ((int)x.size())

using namespace std;
//using namespace atcoder;
using ld = long double;
using ll = long long;
using P = pair<ll, ll>;

template<typename T> bool chmin(T& a, const T& b) { if(a > b){ a = b; return 1;} return 0; }
template<typename T> bool chmax(T& a, const T& b) { if(a < b){ a = b; return 1;} return 0; }

const ll ZER = 0;
const ll MOD = 1e9 + 7;


ll dp[201][20101];
int main(){
    // std::cin.tie(0);
    // std::ios::sync_with_stdio(false);

    int n;
    cin >> n;
    vector<int> s(n), t(n);
    rep(i, n)cin >> s[i];
    rep(i, n)cin >> t[i];
    vector<vector<int>> fld(n, vector<int>(n, -1));
    vector<int> tate(n, 0), yoko(n, 0);
    rep(i, n){
        if(s[i] == 0){
            rep(j, n){
                fld[i][j] = 0;
            }
        }
        if(s[i] == 1)continue;
        if(s[i] == 2){
            rep(j, n){
                fld[i][j] = 1;
            }
        }
    }
    rep(i, n){
        if(t[i] == 0){
            rep(j, n){
                fld[j][i] = 0;
            }
        }
        if(t[i] == 1)continue;
        if(t[i] == 2){
            rep(j, n){
                fld[j][i] = 1;
            }
        }
    }
    int cnt = 0;
    rep(i, n){
        rep(j, n){
            if(fld[i][j] == 1){
                cnt++;
                tate[i] = 1;
                yoko[j] = 1;
            }
        }
    }
    int cnt1 = 0, cnt2 = 0;
    rep(i, n){
        if(s[i] == 1)cnt1 += 1 - tate[i];
        if(t[i] == 1)cnt2 += 1 - yoko[i];
    }
    // cout << cnt1 << " " << cnt2 << " " << cnt << endl;
    cout << max(cnt1, cnt2) + cnt << endl;
}