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

dp = [-1 for _ in range(n)]
V = [[] for _ in range(n)]

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

def f(x):
    if dp[x] != -1:
        return dp[x]

    t = 0
    for v in V[x]:
        t = max(t, f(v)+1)

    dp[x] = t
    return t

t = 0
for i in range(n):
    t = max(t, f(i))

print(t)


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

n, m = map(int, input().split())

dp = [-1 for _ in range(n)]
V = [[] for _ in range(n)]

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

def f(x):
    if dp[x] != -1:
        return dp[x]

    t = 0
    for v in V[x]:
        t = max(t, f(v)+1)

    dp[x] = t
    return dp[x]

t = 0
for i in range(n):
    t = max(t, f(i))

print(t)

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

dp = [-1]*n
V = [[] for _ in range(n)]

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

def f(x):
    if dp[x] != -1:
        return dp[x]

    t = 0
    for v in V[x]:
        t = max(t, f(v)+1)

    dp[x] = t
    return t

t = 0
for i in range(n):
    t = max(t, f(i))

print(t)


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

n, m = map(int, input().split())

dp = [-1 for _ in range(n)]
V = [[] for _ in range(n)]

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

def f(x):
    if dp[x] != -1:
        return dp[x]

    t = 0
    for v in V[x]:
        t = max(t, f(v)+1)

    dp[x] = t
    return dp[x]

t = 0
for i in range(n):
    t = max(t, f(i))

print(t)

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

    t = 0
    for v in V[x]:
        t = max(t, f(v)+1)

    dp[x] = t
    return t

n, m = map(int, input().split())

dp = [-1]*n
V = [[] for _ in range(n)]

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

t = 0
for i in range(n):
    t = max(t, f(i))

print(t)


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

n, m = map(int, input().split())

dp = [-1 for _ in range(n)]
V = [[] for _ in range(n)]

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

def f(x):
    if dp[x] != -1:
        return dp[x]

    t = 0
    for v in V[x]:
        t = max(t, f(v)+1)

    dp[x] = t
    return dp[x]

t = 0
for i in range(n):
    t = max(t, f(i))

print(t)

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

    t = 0
    for v in V[x]:
        t = max(t, f(v)+1)

    dp[x] = t
    return t

n, m = map(int, input().split())

dp = [-1]*(n+1)
V = [[] for _ in range(n+1)]

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

t = 0
for i in range(1, n+1):
    t = max(t, f(i))

print(t)


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

n, m = map(int, input().split())

dp = [-1 for _ in range(n)]
V = [[] for _ in range(n)]

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

def f(x):
    if dp[x] != -1:
        return dp[x]

    t = 0
    for v in V[x]:
        t = max(t, f(v)+1)

    dp[x] = t
    return dp[x]

t = 0
for i in range(n):
    t = max(t, f(i))

print(t)

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

dp = [-1]*(n+1)
V = [[] for _ in range(n+1)]

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

def f(x):
    if dp[x] != -1:
        return dp[x]

    t = 0
    for v in V[x]:
        t = max(t, f(v)+1)

    dp[x] = t
    return dp[x]


t = 0
for i in range(1, n+1):
    t = max(t, f(i))

print(t)


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

n, m = map(int, input().split())

dp = [-1 for _ in range(n)]
V = [[] for _ in range(n)]

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

def f(x):
    if dp[x] != -1:
        return dp[x]

    t = 0
    for v in V[x]:
        t = max(t, f(v)+1)

    dp[x] = t
    return dp[x]

t = 0
for i in range(n):
    t = max(t, f(i))

print(t)

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

    t = 0
    for v in V[x]:
        t = max(t, f(v)+1)

    dp[x] = t
    return dp[x]

n, m = map(int, input().split())

dp = [-1]*(n+1)
V = [[] for _ in range(n+1)]

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

t = 0
for i in range(1, n+1):
    t = max(t, f(i))

print(t)


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

n, m = map(int, input().split())

dp = [-1 for _ in range(n)]
V = [[] for _ in range(n)]

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

def f(x):
    if dp[x] != -1:
        return dp[x]

    t = 0
    for v in V[x]:
        t = max(t, f(v)+1)

    dp[x] = t
    return dp[x]

t = 0
for i in range(n):
    t = max(t, f(i))

print(t)

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

    t = 0
    for v in V[x][1]:
        t = max(t, f(v)+1)

    dp[x] = t
    return dp[x]

n, m = map(int, input().split())

dp = [-1]*(n+1)
V = [[i, []] for i in range(n+1)]

for i in range(m):
    x, y = map(int, input().split())
    V[x][1].append(y)

t = 0
for i in range(1, n+1):
    t = max(t, f(i))
print(t)


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

n, m = map(int, input().split())

dp = [-1 for _ in range(n)]
V = [[] for _ in range(n)]

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

def f(x):
    if dp[x] != -1:
        return dp[x]

    t = 0
    for v in V[x]:
        t = max(t, f(v)+1)

    dp[x] = t
    return dp[x]

t = 0
for i in range(n):
    t = max(t, f(i))

print(t)