#include<bits/stdc++.h>

using namespace std;

int n;
int points_to[50005];
int value[50005];
bool visited[50005];
bool visited_its[50005];
bool in_loop[50005];

void set_loop(int start)
{
    unordered_set<int> vis_loop;
    int current = start;
    while(vis_loop.find(current) == vis_loop.end()){
        in_loop[current] = true;
        vis_loop.insert(current);
        current = points_to[current];
    }
    int siz = vis_loop.size();
    for(auto vis : vis_loop){
        value[vis] = siz - 1;
    }
}

int dfs(int current)
{
    visited[current] = true;
    visited_its[current] = true;
    if(visited_its[points_to[current]]){
        set_loop(current);
        return value[current];
    }
    dfs(points_to[current]);
    if(in_loop[current]){
         return value[current];
    }
    else{
        value[current] = value[points_to[current]] + 1;
        return value[current];
    }
}

int main()
{
    int b;
    cin>>n;
    memset(visited, 0, sizeof(visited));
    memset(in_loop, 0, sizeof(in_loop));
    memset(value, 0, sizeof(value));
    for(int i = 0; i < n; i++){
        points_to[i] = -1;
    }
    for(int i = 0; i < n; i++){
        cin>>b;
        points_to[i] = b-1;
    }
    for(int i = 0; i < n; i++){
        if(!visited[i]){
            memset(visited_its, 0, sizeof(visited_its));
            dfs(i);
        }
    }
    int ans_val = -1;
    for(int i = 0; i < n; i++){
        ans_val = max(ans_val, value[i]);
    }
    cout<<ans_val + 1<<"\n";

    return 0;
}