#include <fstream>
#include <iostream>
using namespace std;
ifstream fin ("inaltime.in");
ofstream fout ("inaltime.out");
int n, k, v[101], tata[101], i, j;
int main()
{
    int radacina, contor;
    fin >> n;
    for (int i=1; i<=n; i++)
    {
        fin >> tata[i];
        if (!tata[i])
            radacina=i;
    }
    int H=0;
    for (int i=1; i<=n; i++)
    {
        contor=1;
        j=i;
        while (j!=radacina)
        {
            contor ++;
            j=tata[j];
        }
        if (contor> H)
            H=contor;
    }
    fout << H;
    return 0;
}