Buggy python submission (verdict: Runtime Error):
#!/usr/bin/env python3

#import
#import math
#import numpy as np
N, M = map(int, input().split())
xy = [list(map(int, input().split())) for _ in range(M)]

G = {i: [] for i in range(1, N + 1)}

for x, y in xy:
    G[x].append(y)

dp = [-1] * (N + 1)

def dfs(num):
    if dp[num] != -1:
        return dp[num]

    t = 0

    for g in G[num]:
        t = max(t, dfs(g) + 1)

    dp[num] = t
    return t

ans = 0
for i in range(1, N + 1):
    ans = max(ans, dfs(i))

print(ans)

Fixed submission:
import sys
sys.setrecursionlimit(10**7)

#import math
#import numpy as np
#= int(input())
#= input()
#= map(int, input().split())
#= list(map(int, input().split()))
#= [input(), input()]
def dfs(num):
    if dp[num] != -1:
        return dp[num]

    res = 0
    for obj in G[num]:
        res = max(res, dfs(obj) + 1)

    dp[num] = res
    return res


N, M = map(int, input().split())

dp = [-1] * N
G = {i:[] for i in range(N)}

for _ in range(M):
    x, y = map(int, input().split())
    G[x - 1].append(y - 1)

res = 0
for i in range(N):
    res = max(res, dfs(i))

print(res)

Buggy python submission (verdict: Runtime Error):
#import
#import math
#import numpy as np
#= int(input())
#= input()
#= map(int, input().split())
#= list(map(int, input().split()))
#= [input(), input()]
def dfs(num):
    if dp[num] != -1:
        return dp[num]

    res = 0
    if len(G[num]) != 0:
        for obj in G[num]:
            res = max(res, dfs(obj) + 1)

    dp[num] = res
    return res


N, M = map(int, input().split())

dp = [-1] * N
G = {i:[] for i in range(N)}

for _ in range(M):
    x, y = map(int, input().split())
    G[x - 1].append(y - 1)

res = 0
for i in range(N):
    res = max(res, dfs(i))

print(res)

Fixed submission:
import sys
sys.setrecursionlimit(10**7)

#import math
#import numpy as np
#= int(input())
#= input()
#= map(int, input().split())
#= list(map(int, input().split()))
#= [input(), input()]
def dfs(num):
    if dp[num] != -1:
        return dp[num]

    res = 0
    for obj in G[num]:
        res = max(res, dfs(obj) + 1)

    dp[num] = res
    return res


N, M = map(int, input().split())

dp = [-1] * N
G = {i:[] for i in range(N)}

for _ in range(M):
    x, y = map(int, input().split())
    G[x - 1].append(y - 1)

res = 0
for i in range(N):
    res = max(res, dfs(i))

print(res)

Buggy python submission (verdict: Runtime Error):
def dfs(num):
    if dp[num] != -1:
        return dp[num]

    res = 0
    for obj in G[num]:
        res = max(res, dfs(obj) + 1)

    dp[num] = res
    return res


N, M = map(int, input().split())

dp = [-1] * (N + 1)
G = {i:[] for i in range(N + 1)}

for _ in range(M):
    x, y = map(int, input().split())
    G[x - 1].append(y - 1)

res = 0
for i in range(N):
    res = max(res, dfs(i))

print(res)

Fixed submission:
import sys
sys.setrecursionlimit(10**7)

#import math
#import numpy as np
#= int(input())
#= input()
#= map(int, input().split())
#= list(map(int, input().split()))
#= [input(), input()]
def dfs(num):
    if dp[num] != -1:
        return dp[num]

    res = 0
    for obj in G[num]:
        res = max(res, dfs(obj) + 1)

    dp[num] = res
    return res


N, M = map(int, input().split())

dp = [-1] * N
G = {i:[] for i in range(N)}

for _ in range(M):
    x, y = map(int, input().split())
    G[x - 1].append(y - 1)

res = 0
for i in range(N):
    res = max(res, dfs(i))

print(res)

Buggy python submission (verdict: Runtime Error):
def dfs(num):
    if dp[num] != -1:
        return dp[num]

    res = 0
    for obj in G[num]:
        res = max(res, dfs(obj) + 1)

    dp[num] = res
    return res


N, M = map(int, input().split())

dp = [-1] * N
G = {i:[] for i in range(N)}

for _ in range(M):
    x, y = map(int, input().split())
    G[x - 1].append(y - 1)

res = 0
for i in range(N):
    res = max(res, dfs(i))

print(res)

Fixed submission:
import sys
sys.setrecursionlimit(10**7)

#import math
#import numpy as np
#= int(input())
#= input()
#= map(int, input().split())
#= list(map(int, input().split()))
#= [input(), input()]
def dfs(num):
    if dp[num] != -1:
        return dp[num]

    res = 0
    for obj in G[num]:
        res = max(res, dfs(obj) + 1)

    dp[num] = res
    return res


N, M = map(int, input().split())

dp = [-1] * N
G = {i:[] for i in range(N)}

for _ in range(M):
    x, y = map(int, input().split())
    G[x - 1].append(y - 1)

res = 0
for i in range(N):
    res = max(res, dfs(i))

print(res)

Buggy python submission (verdict: Runtime Error):
dp = [-1] * N
def dfs(num):
    if dp[num] != -1:
        return dp[num]

    res = 0
    for obj in G[num]:
        res = max(res, dfs(obj) + 1)

    dp[num] = res
    return res


N, M = map(int, input().split())

G = {i:[] for i in range(N)}

for _ in range(M):
    x, y = map(int, input().split())
    G[x - 1].append(y - 1)

res = 0
for i in range(N):
    res = max(res, dfs(i))

print(res)

Fixed submission:
import sys
sys.setrecursionlimit(10**7)

#import math
#import numpy as np
#= int(input())
#= input()
#= map(int, input().split())
#= list(map(int, input().split()))
#= [input(), input()]
def dfs(num):
    if dp[num] != -1:
        return dp[num]

    res = 0
    for obj in G[num]:
        res = max(res, dfs(obj) + 1)

    dp[num] = res
    return res


N, M = map(int, input().split())

dp = [-1] * N
G = {i:[] for i in range(N)}

for _ in range(M):
    x, y = map(int, input().split())
    G[x - 1].append(y - 1)

res = 0
for i in range(N):
    res = max(res, dfs(i))

print(res)

Buggy python submission (verdict: Runtime Error):
N, M = map(int, input().split())

G = {i:[] for i in range(1, N + 1)}

for _ in range(M):
    x, y = map(int, input().split())
    G[x].append(y)

def dfs(num):
    if dp[num] != -1:
        return dp[num]

    res = 0
    for obj in G[num]:
        res = max(res, dfs(obj) + 1)

    dp[num] = res
    return res

dp = [-1] * (N + 1)

res = 0
for i in range(1, N + 1):
    res = max(res, dfs(i))

print(res)


Fixed submission:
import sys
sys.setrecursionlimit(10**7)

#import math
#import numpy as np
#= int(input())
#= input()
#= map(int, input().split())
#= list(map(int, input().split()))
#= [input(), input()]
def dfs(num):
    if dp[num] != -1:
        return dp[num]

    res = 0
    for obj in G[num]:
        res = max(res, dfs(obj) + 1)

    dp[num] = res
    return res


N, M = map(int, input().split())

dp = [-1] * N
G = {i:[] for i in range(N)}

for _ in range(M):
    x, y = map(int, input().split())
    G[x - 1].append(y - 1)

res = 0
for i in range(N):
    res = max(res, dfs(i))

print(res)

Buggy python submission (verdict: Runtime Error):
N, M = map(int, input().split())

G = {i:[] for i in range(1, N + 1)}

for i in range(M):
    x, y = map(int, input().split())
    G[x].append(y)

def dfs(num):
    if dp[num] != -1:
        return dp[num]

    res = 0
    for obj in G[num]:
        res = max(res, dfs(obj) + 1)

    dp[num] = res
    return res

dp = [-1] * (N + 1)

res = 0
for i in range(1, N + 1):
    res = max(res, dfs(i))

print(res)

Fixed submission:
import sys
sys.setrecursionlimit(10**7)

#import math
#import numpy as np
#= int(input())
#= input()
#= map(int, input().split())
#= list(map(int, input().split()))
#= [input(), input()]
def dfs(num):
    if dp[num] != -1:
        return dp[num]

    res = 0
    for obj in G[num]:
        res = max(res, dfs(obj) + 1)

    dp[num] = res
    return res


N, M = map(int, input().split())

dp = [-1] * N
G = {i:[] for i in range(N)}

for _ in range(M):
    x, y = map(int, input().split())
    G[x - 1].append(y - 1)

res = 0
for i in range(N):
    res = max(res, dfs(i))

print(res)