// lanqiao 182 小朋友崇拜圈
#include<bits/stdc++.h>
using namespace std;
const int N = 1e5 + 10;
int n, a[N], dfn[N], idx, mindfn;

int dfs(int x){
    dfn[x] = ++idx;
    if(dfn[a[x]]){
        if(dfn[a[x]] >= mindfn) return dfn[x] - dfn[a[x]] + 1;
        return 0;
    }
    return dfs(a[x]);
}

int main(){
    ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    cin >> n;
    for(int i = 1; i <= n; i++) cin >> a[i];
    int ans = 0;
    for(int i = 1; i <= n; i++){
        if(!dfn[i]){
            mindfn = idx + 1;
            ans = max(ans, dfs(i));
        }
    }
    cout << ans << endl;
    return 0;
}
/* test samples 
9
3 4 2 5 3 8 4 6 9
*/