Buggy python submission (verdict: Time Limit Exceeded):
import bisect, copy, heapq, math, sys
from collections import *
from functools import lru_cache
from itertools import accumulate, combinations, permutations, product
def input():
    return sys.stdin.readline()[:-1]
def ruiseki(lst):
    return [0]+list(accumulate(lst))
def celi(a,b):
    return -(-a//b)
sys.setrecursionlimit(5000000)
mod=pow(10,9)+7
al=[chr(ord('a') + i) for i in range(26)]
direction=[[1,0],[0,1],[-1,0],[0,-1]]

def main():
    n=int(input())
    a=[int(input()) for i in range(n-1)]
    # print(a)
    dic={}
    for i in range(n-1):
        p=a[i]
        if p in dic:
            dic[p].append(i+2)
        else:
            dic[p]=[i+2]


    lst=[-1]*(n+1)

    def solve(m):
        if lst[m]!=-1:
            return lst[m]
        tmp=[]
        if m in dic:

            for i in dic[m]:
                tmp.append(solve(i))
        tmp.sort(reverse=True)
        rtn=0
        for i in range(len(tmp)):
            rtn=max(rtn,tmp[i]+i+1)
        lst[m]=rtn
        return rtn

    solve(1)
    # print(lst)
    print(max(lst))
main()

Fixed submission:
import bisect, copy, heapq, math, sys
from collections import *
from functools import lru_cache
from itertools import accumulate, combinations, permutations, product
def input():
    return sys.stdin.readline()[:-1]
def ruiseki(lst):
    return [0]+list(accumulate(lst))
def celi(a,b):
    return -(-a//b)
sys.setrecursionlimit(5000000)
mod=pow(10,9)+7
al=[chr(ord('a') + i) for i in range(26)]
direction=[[1,0],[0,1],[-1,0],[0,-1]]

def main():
    n=int(input())
    a=[int(input()) for i in range(n-1)]
    # print(a)
    dic={}
    for i in range(n-1):
        p=a[i]
        if p in dic:
            dic[p].append(i+2)
        else:
            dic[p]=[i+2]


    lst=[-1]*(n+1)

    def solve(m):
        if lst[m]!=-1:
            return lst[m]
        tmp=[]
        if m in dic:

            for i in dic[m]:
                tmp.append(solve(i))
        tmp.sort(reverse=True)
        rtn=0
        for i in range(len(tmp)):
            rtn=max(rtn,tmp[i]+i+1)
        lst[m]=rtn
        return rtn

    solve(1)
    # print(lst)
    print(max(lst))
main()

Buggy python submission (verdict: Time Limit Exceeded):
import bisect, copy, heapq, math, sys
from collections import *
from functools import lru_cache
from itertools import accumulate, combinations, permutations, product
def input():
    return sys.stdin.readline()[:-1]
def ruiseki(lst):
    return [0]+list(accumulate(lst))
def celi(a,b):
    return -(-a//b)
sys.setrecursionlimit(5000000)
mod=pow(10,9)+7
al=[chr(ord('a') + i) for i in range(26)]
direction=[[1,0],[0,1],[-1,0],[0,-1]]

def main():
    n=int(input())
    a=[int(input()) for i in range(n-1)]
    # print(a)
    dic=defaultdict(list)
    for i in range(n-1):
        p=a[i]
        dic[p].append(i+2)
    # print(dic)

    lst=[-1]*(n+1)

    def solve(m):
        if lst[m]!=-1:
            return lst[m]
        tmp=[]
        for i in dic[m]:
            tmp.append(solve(i))
        tmp.sort(reverse=True)
        rtn=0
        for i in range(len(tmp)):
            rtn=max(rtn,tmp[i]+i+1)
        lst[m]=rtn
        return rtn

    solve(1)
    # print(lst)
    print(max(lst))
main()

Fixed submission:
import bisect, copy, heapq, math, sys
from collections import *
from functools import lru_cache
from itertools import accumulate, combinations, permutations, product
def input():
    return sys.stdin.readline()[:-1]
def ruiseki(lst):
    return [0]+list(accumulate(lst))
def celi(a,b):
    return -(-a//b)
sys.setrecursionlimit(5000000)
mod=pow(10,9)+7
al=[chr(ord('a') + i) for i in range(26)]
direction=[[1,0],[0,1],[-1,0],[0,-1]]

def main():
    n=int(input())
    a=[int(input()) for i in range(n-1)]
    # print(a)
    dic={}
    for i in range(n-1):
        p=a[i]
        if p in dic:
            dic[p].append(i+2)
        else:
            dic[p]=[i+2]


    lst=[-1]*(n+1)

    def solve(m):
        if lst[m]!=-1:
            return lst[m]
        tmp=[]
        if m in dic:

            for i in dic[m]:
                tmp.append(solve(i))
        tmp.sort(reverse=True)
        rtn=0
        for i in range(len(tmp)):
            rtn=max(rtn,tmp[i]+i+1)
        lst[m]=rtn
        return rtn

    solve(1)
    # print(lst)
    print(max(lst))
main()

Buggy python submission (verdict: Runtime Error):
import bisect, copy, heapq, math, sys
from collections import *
from functools import lru_cache
from itertools import accumulate, combinations, permutations, product
def input():
    return sys.stdin.readline()[:-1]
def ruiseki(lst):
    return [0]+list(accumulate(lst))
def celi(a,b):
    return -(-a//b)
sys.setrecursionlimit(5000000)
mod=pow(10,9)+7
al=[chr(ord('a') + i) for i in range(26)]
direction=[[1,0],[0,1],[-1,0],[0,-1]]

def main()
    n=int(input())
    a=[int(input()) for i in range(n-1)]
    # print(a)
    dic=defaultdict(list)
    for i in range(n-1):
        p=a[i]
        dic[p].append(i+2)
    # print(dic)

    lst=[-1]*(n+1)

    def solve(m):
        if lst[m]!=-1:
            return lst[m]
        tmp=[]
        for i in dic[m]:
            tmp.append(solve(i))
        tmp.sort(reverse=True)
        rtn=0
        for i in range(len(tmp)):
            rtn=max(rtn,tmp[i]+i+1)
        lst[m]=rtn
        return rtn

    solve(1)
    # print(lst)
    print(max(lst))
main()

Fixed submission:
import bisect, copy, heapq, math, sys
from collections import *
from functools import lru_cache
from itertools import accumulate, combinations, permutations, product
def input():
    return sys.stdin.readline()[:-1]
def ruiseki(lst):
    return [0]+list(accumulate(lst))
def celi(a,b):
    return -(-a//b)
sys.setrecursionlimit(5000000)
mod=pow(10,9)+7
al=[chr(ord('a') + i) for i in range(26)]
direction=[[1,0],[0,1],[-1,0],[0,-1]]

def main():
    n=int(input())
    a=[int(input()) for i in range(n-1)]
    # print(a)
    dic={}
    for i in range(n-1):
        p=a[i]
        if p in dic:
            dic[p].append(i+2)
        else:
            dic[p]=[i+2]


    lst=[-1]*(n+1)

    def solve(m):
        if lst[m]!=-1:
            return lst[m]
        tmp=[]
        if m in dic:

            for i in dic[m]:
                tmp.append(solve(i))
        tmp.sort(reverse=True)
        rtn=0
        for i in range(len(tmp)):
            rtn=max(rtn,tmp[i]+i+1)
        lst[m]=rtn
        return rtn

    solve(1)
    # print(lst)
    print(max(lst))
main()

Buggy python submission (verdict: Time Limit Exceeded):
import bisect, copy, heapq, math, sys
from collections import *
from functools import lru_cache
from itertools import accumulate, combinations, permutations, product
def input():
    return sys.stdin.readline()[:-1]
def ruiseki(lst):
    return [0]+list(accumulate(lst))
def celi(a,b):
    return -(-a//b)
sys.setrecursionlimit(5000000)
mod=pow(10,9)+7
al=[chr(ord('a') + i) for i in range(26)]
direction=[[1,0],[0,1],[-1,0],[0,-1]]

n=int(input())
a=[int(input()) for i in range(n-1)]
# print(a)
dic=defaultdict(list)
for i in range(n-1):
    p=a[i]
    dic[p].append(i+2)
# print(dic)

lst=[-1]*(n+1)

def solve(m):
    if lst[m]!=-1:
        return lst[m]
    tmp=[]
    for i in dic[m]:
        tmp.append(solve(i))
    tmp.sort(reverse=True)
    rtn=0
    for i in range(len(tmp)):
        rtn=max(rtn,tmp[i]+i+1)
    lst[m]=rtn
    return rtn

solve(1)
# print(lst)
print(max(lst))

Fixed submission:
import bisect, copy, heapq, math, sys
from collections import *
from functools import lru_cache
from itertools import accumulate, combinations, permutations, product
def input():
    return sys.stdin.readline()[:-1]
def ruiseki(lst):
    return [0]+list(accumulate(lst))
def celi(a,b):
    return -(-a//b)
sys.setrecursionlimit(5000000)
mod=pow(10,9)+7
al=[chr(ord('a') + i) for i in range(26)]
direction=[[1,0],[0,1],[-1,0],[0,-1]]

def main():
    n=int(input())
    a=[int(input()) for i in range(n-1)]
    # print(a)
    dic={}
    for i in range(n-1):
        p=a[i]
        if p in dic:
            dic[p].append(i+2)
        else:
            dic[p]=[i+2]


    lst=[-1]*(n+1)

    def solve(m):
        if lst[m]!=-1:
            return lst[m]
        tmp=[]
        if m in dic:

            for i in dic[m]:
                tmp.append(solve(i))
        tmp.sort(reverse=True)
        rtn=0
        for i in range(len(tmp)):
            rtn=max(rtn,tmp[i]+i+1)
        lst[m]=rtn
        return rtn

    solve(1)
    # print(lst)
    print(max(lst))
main()