#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  cin.tie(nullptr)->sync_with_stdio(false);
  int n;
  cin >> n;
  vector<int> a(n);
  rep(i, n) cin >> a[i], a[i]--;
  vector<int> deg(n, 0);
  rep(i, n) if (a[i] != -1) deg[a[i]]++;
  set<int> ans;
  rep(i, n) {
    if (deg[i] == 0)
      if (a[i] != -1)
        if (a[a[i]] != -1)
          ans.insert(a[a[i]]);
  }
  cout << ans.size() << '\n';
  return 0;
}