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

typedef long long ll;
typedef pair<int,int> P;

#define p_ary(ary,a,b) do { cout << "["; for (int count = (a);count < (b);++count) cout << ary[count] << ((b)-1 == count ? "" : ", "); cout << "]\n"; } while(0)
#define p_map(map,it) do {cout << "{";for (auto (it) = map.begin();;++(it)) {if ((it) == map.end()) {cout << "}\n";break;}else cout << "" << (it)->first << "=>" << (it)->second << ", ";}}while(0)

template<typename T1,typename T2>ostream& operator<<(ostream& os,const pair<T1,T2>& a) {os << "(" << a.first << ", " << a.second << ")";return os;}

const char newl = '\n';

int main() {
    int n;
    cin >> n;
    vector<int> s(n),t(n);
    for (int i = 0;i < n;++i) cin >> s[i];
    for (int i = 0;i < n;++i) cin >> t[i];
    vector<vector<bool>> f(n,vector<bool>(n,false));
    for (int i = 0;i < n;++i) if (s[i] == 2) for (int j = 0;j < n;++j) f[i][j] = true;
    for (int i = 0;i < n;++i) if (t[i] == 2) for (int j = 0;j < n;++j) f[j][i] = true;
    int a = 0,b = 0;
    for (int i = 0;i < n;++i) if (s[i] == 1) {
        bool g = false;
        for (int j = 0;j < n;++j) if (f[i][j]) g = true;
        if (!g) a++;
    }
    for (int i = 0;i < n;++i) if (t[i] == 1) {
        bool g = false;
        for (int j = 0;j < n;++j) if (f[j][i]) g = true;
        if (!g) b++;
    }
    int cnt = 0;
    for (int i = 0;i < n;++i) for (int j = 0;j < n;++j) if (f[i][j]) cnt++;
    cout << cnt+max(a,b) << newl;
}