#include <bits/stdc++.h>
#define ll long long int
#define N "\n"
using namespace std;
#include <ext/pb_ds/assoc_container.hpp> 
#include <ext/pb_ds/tree_policy.hpp> 
using namespace __gnu_pbds; 
  
#define ordered_set tree<int, null_type,less_equal<int>, rb_tree_tag,tree_order_statistics_node_update> 
//erase not possible when we are using [less equal]  instead of [less]

//order_of_key (k) : Number of items strictly smaller than k .
//find_by_order(k) : K-th element in a set (counting from zero).
  
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    ll n;
    cin>>n;
    vector<ll>a(n);
    for(ll i=0;i<n;i++){
        cin>>a[i];
    }
    ordered_set s;
    vector<ll>vis(n,0);
    ll ans=0;

    for(ll i=n-1;i>=0;i--){
      ll items=(n-i)-s.order_of_key(a[i])-1;
      if(items>=a[i]){
            ans++;
            vis[i]=1;
      }
      s.insert(a[i]);
    }
    s.clear();
    for(ll i=0;i<n;i++){
      if(vis[i]==0){
            ll items=s.order_of_key(a[i]+1);
            if(items>=a[i]){
                  ans++;
            }
      }
      s.insert(a[i]);
    }
    cout<<ans<<N;
    return 0;
}