#include<bits/stdc++.h>
using namespace std;
int a[100000];
int f[100000];
int main(){
    freopen("spring.in","r",stdin);
    freopen("spring.out","w",stdout);
    int n,k,s=-1;
    cin>>n;
    for(int i=1;i<=n;i++){
        cin>>a[i];
    }
    for(int i=n;i>0;i--){
      if(i+a[i]>n){
        f[i]=1;
      }
      else{
        f[i]=1+f[i+a[i]];
        }
      if(f[i]>s){
          s=f[i];
        }
      
    }
    cout<<s;
    return 0;
}/*难