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

using ll = long long;

int main()
{
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    int N;
    cin >> N;
    vector<int> P(N);
    for (int i = 0; i < N; i++)
    {
        cin >> P[i];
        P[i]--;
    }

    vector<int> in(N);
    for (int i = 0; i < N; i++)
    {
        if (P[i] == -1) continue;
        in[P[i]]++;
    }

    vector<bool> shiki(N);
    for (int i = 0; i < N; i++)
    {
        if (in[i] == 0)
        {
            if (P[i] != -1 && P[P[i]] != -1)
            {
                shiki[P[P[i]]] = true;
            }
        }
    }

    int ans = 0;
    for (int i = 0; i < N; i++)
    {
        if (shiki[i])
        {
            ans++;
        }
    }

    cout << ans << endl;
}