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

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);

    int N;
    cin >> N;
    vector<int> P(N);
    for (int &x : P)
        cin >> x;

    vector<bool> kami(N);

    for (int i = 0; i < N; ++i)
        if (P[i])
            kami[P[i] - 1] = true;

    vector<bool> shikigami(N);
    for (int i = 0; i < N; ++i)
        if (P[i] && !kami[i])
            shikigami[P[i] - 1] = true;

    vector<bool> ans(N);
    for (int i = 0; i < N; ++i)
        if (P[i] && shikigami[i])
            ans[P[i] - 1] = true;

    cout << ranges::count(ans, true) << endl;
}