using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
class Solution {

    static void Main(String[] args) {
        int n = Convert.ToInt32(Console.ReadLine());
        string[] height_temp = Console.ReadLine().Split(' ');
        int[] height = Array.ConvertAll(height_temp,Int32.Parse);
        
        int tallest = 0;
        for (int i = 0; i <= n-1; i++){
            if (height[i] >= tallest){
                tallest++;
            }
        }
        Console.WriteLine(tallest-1);
    }
}