#include <iostream>
using namespace std;

int main() {
        // your code goes here
        long int n, i;
        long int a[3000001],b[3000001];
        cin >>n;
        for(i = 0; i < n; i++){
                cin >>a[i];
                b[i] = 0;
        }
        long int max = 0, sum = 0;
        for(i=0; i < n; i++){
                sum = sum + 1;
                if(a[i] <=400000){b[i + a[i]]++;}
                sum = sum - b[i];
                if(sum > max){
                        max = sum;
                }
        }
        cout <<max;
        return 0;
}