#include<bits/stdc++.h>

using namespace std;
using ll = long long;


int main()
{
	int n; cin >> n;
	vector<int> s(n), t(n);
	for(auto &i: s)cin >> i;
	for(auto &i: t)cin >> i;
	vector<vector<int>> a(n, vector<int>(n, -1));

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

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

	int h = n, w = n;
	int tat = 0, yok = 0;

	for(int i = 0; i < h; i++) {
		bool has1 = false, hasm = false;
		for(int j = 0; j < w; j++) {
			if(a[i][j] == 1) {
				has1 = true;
			}
			if(a[i][j] == -1) {
				hasm = true;
			}
		}
		if(!has1 && hasm) {
			tat++;
		}
	}

	for(int i = 0; i < w; i++) {
		bool has1 = false, hasm = false;
		for(int j = 0; j < h; j++) {
			if(a[j][i] == 1) {
				has1 = true;
			}
			if(a[j][i] == -1) {
				hasm = true;
			}
		}
		if(!has1 && hasm) {
			yok++;
		}
	}

	int ans = max(tat, yok);
	for(int i = 0; i < h; i++)ans += count_if(a[i].begin(), a[i].end(), [](int a){return a == 1;});
	cout << ans << endl;

}