115A - Party.cpp

/*
A company has n employees numbered from 1 to n. Each employee either has no immediate manager or exactly one immediate manager, who is another employee with a different number. An employee A is said to be the superior of another employee B if at least one of the following is true:

Employee A is the immediate manager of employee B
Employee B has an immediate manager employee C such that employee A is the superior of employee C.
The company will not have a managerial cycle. That is, there will not exist an employee who is the superior of his/her own immediate manager.

Today the company is going to arrange a party. This involves dividing all n employees into several groups: every employee must belong to exactly one group. Furthermore, within any single group, there must not be two employees A and B such that A is the superior of B.

What is the minimum number of groups that must be formed?

Input
The first line contains integer n (1?=?n?=?2000) — the number of employees.

The next n lines contain the integers pi (1?=?pi?=?n or pi?=?-1). Every pi denotes the immediate manager for the i-th employee. If pi is -1, that means that the i-th employee does not have an immediate manager.

It is guaranteed, that no employee will be the immediate manager of him/herself (pi???i). Also, there will be no managerial cycles.

Output
Print a single integer denoting the minimum number of groups that will be formed in the party.

Examples
inputCopy
5
-1
1
2
1
-1
outputCopy
3
Note
For the first example, three groups are sufficient, for example:

Employee 1
Employees 2 and 4
Employees 3 and 5
*/





#include<bits/stdc++.h>
using namespace std;


int main(){
    ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	
	int n;
	cin >> n;
	
	vector <int> v(n);
	
	for (auto &x: v) cin >> x;
	
	int res = 0;
	
	for (int i = 0; i < n; i++) {
		int j = i, cnt = 0;
		while (v[j] != -1) {
			cnt++;
			j = v[j] - 1;
		}
		res = max(res, cnt);
	}
	
	cout << res + 1;

    return 0;
}