A.Party

` import heapq, math from itertools import * from bisect import * from collections import * from sys import stdin, stdout

#####-> Templates <-

def pr(out): return stdout.write(f"{out}\n")

def input(): return stdin.readline().rstrip()

def int_inp(): return int(input())

def inp_int_l(): return list(map(int, stdin.readline().split()))

def inp_l(): return stdin.readline().split()

####################################

def solve(): n = int(input()) graph = [[] for _ in range(n)] indegree = [0] * n for node in range(n): p = int_inp() if p != -1: graph[p — 1].append(node) indegree[node] += 1 level = [[node for node in range(n) if indegree[node] == 0]] queue = deque(level[0]) while queue:

lev = []
    for _ in range(len(queue)):
        node = queue.popleft()
        for nei in graph[node]:
            lev.append(nei)
            queue.append(nei)
    level.append(lev)
count = 0
for l in level:
    if l:
        count += 1

print(count)

if name == "__main__": t = 1 for _ in range(t): solve() ` ~~~~~

~~~~~