#include <bits/stdc++.h>
using namespace std;

int main() {
    int N;
    cin >> N;
    vector<int> P(N + 1);
    vector<int> in_degree(N + 1, 0);
    for (int i = 1; i <= N; i++) {
        cin >> P[i];
        if (P[i] != 0) in_degree[P[i]]++;
    }
    
    vector<bool> is_shikigami(N + 1, false);
    for (int q = 1; q <= N; q++) {
        if (in_degree[q] == 0 && P[q] != 0) {
            int p = P[q];
            if (P[p] != 0) {
                is_shikigami[P[p]] = true;
            }
        }
    }
    
    int count = 0;
    for (int i = 1; i <= N; i++) {
        if (is_shikigami[i]) count++;
    }
    cout << count << endl;
    
    return 0;
}