#include "bits/stdc++.h"
using namespace std;
#define int long long
#define endl '\n'
#define speed cin.tie (0) -> sync_with_stdio (0);ios_base::sync_with_stdio(false);cin.tie(0);
const int maxn = 200005;
int n;
int l[maxn], r[maxn];
int dp[maxn];
int rec(int i)
{
if (i <= 0) return 0;
if (dp[i] != -1) return dp[i];
return dp[i] = max(rec(i - 1), rec(i - l[i]) + 1);
}
void s1()
{
memset(dp, -1, sizeof dp);
cout<<rec(n)<<endl;
}
void s2()
{
cout<<(n - 1) / (l[0] + 1) + 1<<endl;
}
void solve()
{
int mx = 0;
cin>>n;
for(int i=1; i<=n; i++) cin>>l[i];
for(int i=1; i<=n; i++)
{
cin>>r[i];
mx = max(mx, r[i]);
}
if (mx == 0) s1();
else s2();
}
signed main ()
{
speed
// freopen("feast.in", "r", stdin);
// freopen("feast.out", "w", stdout);
int _ = 1;
// cin>>_;
while(_--) solve();
return 0;
}
