#include <iostream>
#include <fstream>
using namespace std;

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

int tata[105],n,i,viz[105],H=0,k,h;

int main()
{
    fin>>n;
    for(i=1;i<=n;i++)
        fin>>tata[i];
    for(i=1;i<=n;i++)
       {
           k=i;h=1;
           while(tata[k]!=0)
           {
               k=tata[k];h++;
           }
           if(h>H)H=h;
       }
    fout<<H;



    return 0;
}