#include <iostream>
#include <bits/stdc++.h>
using namespace std ;
int arr[100005];
int dp[100005];
int calcHight(int node){
    if(dp[node]!=-1)return dp[node];
    if(arr[node]==-1)return dp[node]=0;
    return dp[node]=1+calcHight(arr[node]);
}
int main(){
    int n ;
    cin>>n ;
    for(int i = 0 ; i < n ; i ++) {cin>>arr[i];}
    memset(dp,-1, sizeof(dp));
    for(int i = 0 ; i < n ; i ++){calcHight(i);}
    int ans = INT_MIN;
    for(int i = 0 ; i < n ; i ++){
        ans=max(ans,dp[i]);
        cout<<"node: "<<i <<"   Height "<<  dp[i]<<endl;
    }
    cout<<ans<<endl;
    return 0;
}