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

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n;
    cin >> n;
    vector<vector<int>> g(n);
    vector<int> p(n);
    vector<bool> used(n, false);
    for(int i = 0; i < n; i++){
        cin >> p[i];
        p[i]--;
        if(p[i] == -1) continue;
        used[p[i]] = true;
        g[i].emplace_back(p[i]);
    }
    int ans = 0;
    auto dfs = [&](auto dfs, int v, int p, int dep) -> void {
        if(dep == 2){
            ans++;
            return;
        }
        for(auto u : g[v]){
            if(u == p) continue;
            dfs(dfs, u, v, dep + 1);
        }
    };
    for(int v = 0; v < n; v++){
        if(!used[v]) dfs(dfs, v, -1, 0);
    }
    cout << ans << '\n';
}