#include "bits/stdc++.h"
//#include <atcoder/all>

using namespace std;
//using namespace atcoder;

#define ll long long
ll INF = (1LL << 60);

signed 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<int>>G(N, vector<int>(N));
	vector<bool>okS(N), okT(N);
	for (int i = 0; i < N; i++) {
		if (S[i] == 2) {
			for (int j = 0; j < N; j++) {
				G[i][j] = 1;
				okS[j] = true;
				
			}
		}
		if (T[i] == 2) {
			for(int j = 0; j < N; j++){
				G[j][i] = 1;
				okT[j] = true;
			}
		}
	}
	for (int i = 0; i < N; i++) {
		bool ok = false;
		for (int j = 0; j < N; j++) {
			if (G[i][j] == 1)ok = true;
		}
		if (S[i] == 1 && !ok) {
			for (int j = 0; j < N; j++) {
				if (!okT[j] && T[j] != 0) {
					G[i][j] = 1;
					okS[i] = true;
					okT[j] = true;
					goto t;
				}
			}
			for (int j = 0; j < N; j++) {
				if (okT[j]) {
					G[i][j] = 1;
					okS[i] = true;
					okT[j] = true;
					goto t;
				}
			}
			
		t:;
		}
	
	}
	for (int i = 0; i < N; i++) {
		bool ok = false;
		for (int j = 0; j < N; j++) {
			if (G[j][i] == 1)ok = true;
		}
		if (T[i] == 1 && !ok) {
			for (int j = 0; j < N; j++) {
				if (!okS[j] && S[j] != 0) {
					G[j][i] = 1;
					okS[j] = true;
					okT[i] = true;
					goto f;
				}
			}
			for (int j = 0; j < N; j++) {
				if (okS[j]) {
					G[j][i] = 1;
					okS[j] = true;
					okT[i] = true;
					goto f;
				}
			}
			
		f:;
		}
	}
	int ans = 0;
	for (int i = 0; i < N; i++)for (int j = 0; j < N; j++) {
		if (G[i][j]) {
			ans++;
		}
	}
	cout << ans << endl;
	return 0;
}