#include <bits/stdc++.h>

using namespace std;
vector<vector<int>> g;
vector<long long> dyn;
vector<long long> max_children;
vector<bool> used;
int n;
long long m = 0;

void f(int v) {
    used[v] = true;
    for (auto i: g[v]) {
        if (!used[i]) f(i);
        dyn[v] += max_children[i];
        max_children[v] += max(max_children[i], dyn[i]);
    }

    m = max(dyn[v], m);
}

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

    ofstream fout("select.out");
    ifstream fin("select.in");

    int start;

    fin >> n;
    g.resize(n);
    dyn.resize(n, 1);
    max_children.resize(n);
    used.resize(n+1, false);
    int t;

    for (int i = 0; i < n; i++) {
        fin >> t;
        if (t!= 0) g[t-1].push_back(i);
        else start = i;
    }

    f(start);

    fout << max(max_children[start], dyn[start]);

    return 0;
}