#include <iostream>
#include <string>
#include <vector>
#include <cmath>
#include <algorithm>
#include <cstdlib>
#include <ctime>
#include <cstdio>
#include <functional>
#include <set>
#include <sstream>
#include <map>
#include <queue>
#include <stack>

using namespace std;


const long long mod=1000000007; 

int main()
{
	int n;
	cin>>n;
	int x;
	cin>>x;
	int rest=x-1;
	
	int res=0;
	for(int i=1;i<n;i++){
		int a;
		scanf("%d",&a);
		if(rest==0) x=a,rest=x-1;
		else if(x>a){
			res++;
			rest--;
		}
	}
	cout<<res<<endl;


    return 0;
}