#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000005
#define Inf64 1000000000000000001LL

int main(){
	
	int n;
	cin>>n;
	
	vector<int> p(n);
	vector<int> cnt(n);
	rep(i,n){
		cin>>p[i];
		p[i]--;
		if(p[i]>=0){
			cnt[p[i]]++;
		}
	}
	set<int> s;
	rep(i,n){
		if(cnt[i]==0){
			int t = p[i];
			if(t>=0){
				t = p[t];
				if(t>=0)s.insert(t);
			}
		}
	}
	cout<<s.size()<<endl;
	return 0;
}