Buggy python submission (verdict: Runtime Error):
import sys
import os
f = open('../../input.txt', 'r')
sys.stdin = f

from sys import setrecursionlimit
setrecursionlimit(10 ** 7)

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

xy_dict = {}
for i in range(1,n+1):
    xy_dict[i] = []

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

dp = [-1]*(n+1)
dp[0] = 0

def get_longest(x):
    global dp

    if( dp[x] >= 0):
        return dp[x]
    else:
        y_list = xy_dict[x]
        temp_max = 0
        for y in y_list:
            temp_max = max(temp_max, get_longest(y)+1)

        dp[x] = temp_max
        return temp_max

ans = 0
for i in range(1,n+1):
    ans = max(ans, get_longest(i))

print(ans)


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

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

xy_dict = {}
for i in range(1,n+1):
    xy_dict[i] = []

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

dp = [-1]*(n+1)
dp[0] = 0

def get_longest(x):
    global dp

    if( dp[x] >= 0):
        return dp[x]
    else:
        y_list = xy_dict[x]
        temp_max = 0
        for y in y_list:
            temp_max = max(temp_max, get_longest(y)+1)

        dp[x] = temp_max
        return temp_max

ans = 0
for i in range(1,n+1):
    ans = max(ans, get_longest(i))

print(ans)

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

xy_dict = {}
for i in range(1,n+1):
    xy_dict[i] = []

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

dp = [-1]*(n+1)
dp[0] = 0

def get_longest(x):
    # global dp

    if( dp[x] >= 0):
        return dp[x]
    else:
        y_list = xy_dict[x]
        temp_max = 0
        for y in y_list:
            temp_max = max(temp_max, get_longest(y)+1)

        dp[x] = temp_max
        return temp_max

ans = 0
for i in range(1,n+1):
    ans = max(ans, get_longest(i))

print(ans)

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

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

xy_dict = {}
for i in range(1,n+1):
    xy_dict[i] = []

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

dp = [-1]*(n+1)
dp[0] = 0

def get_longest(x):
    global dp

    if( dp[x] >= 0):
        return dp[x]
    else:
        y_list = xy_dict[x]
        temp_max = 0
        for y in y_list:
            temp_max = max(temp_max, get_longest(y)+1)

        dp[x] = temp_max
        return temp_max

ans = 0
for i in range(1,n+1):
    ans = max(ans, get_longest(i))

print(ans)

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

xy_dict = {}
for i in range(1,n+1):
    xy_dict[i] = []

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

dp = [-1]*(n+1)
dp[0] = 0

def get_longest(x):
    global dp

    if( dp[x] >= 0):
        return dp[x]
    else:
        y_list = xy_dict[x]
        temp_max = 0
        for y in y_list:
            temp_max = max(temp_max, get_longest(y)+1)

        dp[x] = temp_max
        return temp_max

ans = 0
for i in range(1,n+1):
    ans = max(ans, get_longest(i))

print(ans)

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

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

xy_dict = {}
for i in range(1,n+1):
    xy_dict[i] = []

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

dp = [-1]*(n+1)
dp[0] = 0

def get_longest(x):
    global dp

    if( dp[x] >= 0):
        return dp[x]
    else:
        y_list = xy_dict[x]
        temp_max = 0
        for y in y_list:
            temp_max = max(temp_max, get_longest(y)+1)

        dp[x] = temp_max
        return temp_max

ans = 0
for i in range(1,n+1):
    ans = max(ans, get_longest(i))

print(ans)

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

xy_dict = {}
for i in range(1,n+1):
    xy_dict[i] = []

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

dp = [-1]*(n+1)
dp[0] = 0

def get_longest(x):
    global dp

    if( dp[x] > 0):
        return dp[x]
    else:
        y_list = xy_dict[x]
        temp_max = 0
        for y in y_list:
            temp_max = max(temp_max, get_longest(y)+1)

        dp[x] = temp_max
        return temp_max

for i in range(1,n+1):
    get_longest(i)

print(max(dp))

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

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

xy_dict = {}
for i in range(1,n+1):
    xy_dict[i] = []

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

dp = [-1]*(n+1)
dp[0] = 0

def get_longest(x):
    global dp

    if( dp[x] >= 0):
        return dp[x]
    else:
        y_list = xy_dict[x]
        temp_max = 0
        for y in y_list:
            temp_max = max(temp_max, get_longest(y)+1)

        dp[x] = temp_max
        return temp_max

ans = 0
for i in range(1,n+1):
    ans = max(ans, get_longest(i))

print(ans)

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

xy_dict = {}
for i in range(1,n+1):
    xy_dict[i] = []

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

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

def get_longest(x):
    global dp

    if( dp[x] > 0):
        return dp[x]
    else:
        y_list = xy_dict[x]
        temp_max = 0
        for y in y_list:
            temp_max = max(temp_max, get_longest(y)+1)

        dp[x] = temp_max
        return temp_max

for i in range(1,n+1):
    get_longest(i)

print(max(dp))

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

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

xy_dict = {}
for i in range(1,n+1):
    xy_dict[i] = []

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

dp = [-1]*(n+1)
dp[0] = 0

def get_longest(x):
    global dp

    if( dp[x] >= 0):
        return dp[x]
    else:
        y_list = xy_dict[x]
        temp_max = 0
        for y in y_list:
            temp_max = max(temp_max, get_longest(y)+1)

        dp[x] = temp_max
        return temp_max

ans = 0
for i in range(1,n+1):
    ans = max(ans, get_longest(i))

print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
n, m = map(int, input().split())
xy = [list(map(int, input().split())) for _ in range(m)]

dp = [[0,0] for _ in range(n+1)]

check = True
while(check):
    check = False
    for i in range(m):
        x, y  =xy[i]
        if(dp[x][1] < dp[y][1]+1):
            dp[x][1] =  dp[y][1]+1
            check = True
        if(dp[y][0] < dp[x][0]+1):
            dp[y][0] = dp[x][0]+1
            check = True

ans = 0
for i in range(n+1):
     ans = max(ans, dp[i][0])

print(ans)

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

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

xy_dict = {}
for i in range(1,n+1):
    xy_dict[i] = []

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

dp = [-1]*(n+1)
dp[0] = 0

def get_longest(x):
    global dp

    if( dp[x] >= 0):
        return dp[x]
    else:
        y_list = xy_dict[x]
        temp_max = 0
        for y in y_list:
            temp_max = max(temp_max, get_longest(y)+1)

        dp[x] = temp_max
        return temp_max

ans = 0
for i in range(1,n+1):
    ans = max(ans, get_longest(i))

print(ans)