Buggy python submission (verdict: Runtime Error):
import collections

def dfs(v):
    if cache.get(v):
        return cache[v]
    path=0
    for adj in g[v]:
        path=max(path,1+dfs(adj))
    cache[v]=path
    return path


n,m=map(int,input().split())
g=collections.defaultdict(list)
cache={}
path=0
for _ in range(m):
    u,v=map(int,input().split())
    g[u].append(v)
for v in range(1,n+1):
    path=max(path,dfs(v))
print(path)



Fixed submission:
import collections
import sys
sys.setrecursionlimit(10**9)
cache,edge={},collections.defaultdict(list)
def dp(node):
  if node in cache:
    return cache[node]
  lcl_max=0
  for child in edge[node]:
    
    lcl_max=max(lcl_max,1+dp(child))
  cache[node]=lcl_max
  return lcl_max
 
max_dis=0

n,m=map(int,input().split())
for _ in range(m):
  a,b=map(int,input().split())
  edge[a].append(b)
for node in range(1,n+1):
  max_dis=max(max_dis,dp(node))
print(max_dis)

Buggy python submission (verdict: Runtime Error):
import collections
import sys
sys.setrecursionlimit(10**9)
cache,edge={},collections.defaultdict(list)
def dp(node):
  if node in cache:
    return cache[node]
  lcl_max=0
  for child in edge[node]:
    
    lcl_max=max(lcl_max,1+dp(child))
  cache[node]=lcl_max
  return lcl_max
 
max_dis=0

n,m=map(int,input().split())
for _ in range(m):
  a,b=map(int,input().split())
  edge[a].append(b)
for node in range(1,n+1):
  max_dis=max(max_dis,dp(node,cache,edge))
print(max_dis)

Fixed submission:
import collections
import sys
sys.setrecursionlimit(10**9)
cache,edge={},collections.defaultdict(list)
def dp(node):
  if node in cache:
    return cache[node]
  lcl_max=0
  for child in edge[node]:
    
    lcl_max=max(lcl_max,1+dp(child))
  cache[node]=lcl_max
  return lcl_max
 
max_dis=0

n,m=map(int,input().split())
for _ in range(m):
  a,b=map(int,input().split())
  edge[a].append(b)
for node in range(1,n+1):
  max_dis=max(max_dis,dp(node))
print(max_dis)

Buggy python submission (verdict: Runtime Error):
import collections
def dp(node,cache,edge):
  if node in cache:
    return cache[node]
  lcl_max=0
  for child in edge[node]:
    cache[child]=dp(child,cache,edge)
    lcl_max=max(lcl_max,1+cache[child])
  return lcl_max
 
max_dis=0
cache,edge={},collections.defaultdict(list)
n,m=map(int,input().split())
for _ in range(m):
  a,b=map(int,input().split())
  edge[a].append(b)
for node in range(1,n+1):
  max_dis=max(max_dis,dp(node,cache,edge))
 
  

Fixed submission:
import collections
import sys
sys.setrecursionlimit(10**9)
cache,edge={},collections.defaultdict(list)
def dp(node):
  if node in cache:
    return cache[node]
  lcl_max=0
  for child in edge[node]:
    
    lcl_max=max(lcl_max,1+dp(child))
  cache[node]=lcl_max
  return lcl_max
 
max_dis=0

n,m=map(int,input().split())
for _ in range(m):
  a,b=map(int,input().split())
  edge[a].append(b)
for node in range(1,n+1):
  max_dis=max(max_dis,dp(node))
print(max_dis)

Buggy python submission (verdict: Runtime Error):
import collections
def dp(node,cache,edge):
  if node in cache:
    return cache[node]
  lcl_max=0
  for child in edge[node]:
    dp[child]=dp(child,cache,edge)
    lcl_max=max(lcl_max,1+dp[child])
  return lcl_max

max_dis=0
cache,edge={},collections.defaultdict(list)
n,m=map(int,input().split())
for _ in range(m):
  a,b=map(int,input().split())
  edge[a].append(b)
for node in range(1,n+1):
  max_dis=max(max_dis,dp(node,cache,edge))

  
  


Fixed submission:
import collections
import sys
sys.setrecursionlimit(10**9)
cache,edge={},collections.defaultdict(list)
def dp(node):
  if node in cache:
    return cache[node]
  lcl_max=0
  for child in edge[node]:
    
    lcl_max=max(lcl_max,1+dp(child))
  cache[node]=lcl_max
  return lcl_max
 
max_dis=0

n,m=map(int,input().split())
for _ in range(m):
  a,b=map(int,input().split())
  edge[a].append(b)
for node in range(1,n+1):
  max_dis=max(max_dis,dp(node))
print(max_dis)