#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];
int ret = max(rec(i - 1), rec(i - l[i] - 1) + 1);
return dp[i] = ret;
}
void s1()
{
for(int i=1; i<=maxn-5; i++) dp[i] = -1;
cout<<rec(n)<<endl;
}
void s2()
{
cout<<(n - 1) / (l[1] + 1) + 1<<endl;
}
void solve()
{
bool ok = 1;
cin>>n;
for(int i=1; i<=n; i++) cin>>l[i];
for(int i=1; i<=n; i++)
{
cin>>r[i];
ok &= (l[i] == r[i]); ok &= (l[i] == l[1]);
}
if (ok) s2();
else s1();
}
signed main ()
{
speed
// freopen("feast.in", "r", stdin);
// freopen("feast.out", "w", stdout);
int _ = 1;
// cin>>_;
while(_--) solve();
return 0;
}
