Buggy python submission (verdict: Runtime Error):
import sys
sys.setrecursionlimit(10**9+7)
def check(graph,seen,now):
    seen[now] = True 
    for i in range(len(graph[now])):
        if seen[i] :
            continue
        if graph[now][i] == 0 :
            continue
        check(graph,seen,i)
    return seen


#入力
N,M = map(int,input().split())
para = [[i for i in map(int,input().split())] for j in range(M)]
graph =[[0 for i in range(N)] for  j in range(M)]
for i in range(M):
    graph[para[i][0]-1][para[i][1]-1] = 1
    graph[para[i][1]-1][para[i][0]-1] = 1 

#seen = [False]*(N)
ans = 0
for i in range(M):
    seen = [False]*(N)
    graph[para[i][0]-1][para[i][1]-1] = 0
    graph[para[i][1]-1][para[i][0]-1] = 0
    if False in check(graph,seen,0):
        ans += 1
    graph[para[i][0]-1][para[i][1]-1] = 1
    graph[para[i][1]-1][para[i][0]-1] = 1 
print(ans)


Fixed submission:
def check(graph,seen,now):
    seen[now] = True 
    for i in range(len(graph[now])):
        if seen[i] :
            continue
        if graph[now][i] == 0 :
            continue
        check(graph,seen,i)
    return seen


#入力
N,M = map(int,input().split())
para = [[i for i in map(int,input().split())] for j in range(M)]
graph =[[0 for i in range(N)] for  j in range(N)]
for i in range(M):
    graph[para[i][0]-1][para[i][1]-1] = 1
    graph[para[i][1]-1][para[i][0]-1] = 1 

#seen = [False]*(N)
ans = 0
for i in range(M):
    seen = [False]*(N)
    graph[para[i][0]-1][para[i][1]-1] = 0
    graph[para[i][1]-1][para[i][0]-1] = 0
    if False in check(graph,seen,0):
        ans += 1
    graph[para[i][0]-1][para[i][1]-1] = 1
    graph[para[i][1]-1][para[i][0]-1] = 1 

print(ans)

Buggy python submission (verdict: Runtime Error):
import sys
sys.setrecursionlimit(10000)
def check(graph,seen,now):
    seen[now] = True 
    for i in range(len(graph[now])):
        if seen[i] :
            continue
        if graph[now][i] == 0 :
            continue
        check(graph,seen,i)
    return seen


#入力
N,M = map(int,input().split())
para = [[i for i in map(int,input().split())] for j in range(M)]
graph =[[0 for i in range(N)] for  j in range(M)]
for i in range(M):
    graph[para[i][0]-1][para[i][1]-1] = 1
    graph[para[i][1]-1][para[i][0]-1] = 1 

#seen = [False]*(N)
ans = 0
for i in range(M):
    seen = [False]*(N)
    graph[para[i][0]-1][para[i][1]-1] = 0
    graph[para[i][1]-1][para[i][0]-1] = 0
    if False in check(graph,seen,0):
        ans += 1
    graph[para[i][0]-1][para[i][1]-1] = 1
    graph[para[i][1]-1][para[i][0]-1] = 1 
print(ans)

Fixed submission:
def check(graph,seen,now):
    seen[now] = True 
    for i in range(len(graph[now])):
        if seen[i] :
            continue
        if graph[now][i] == 0 :
            continue
        check(graph,seen,i)
    return seen


#入力
N,M = map(int,input().split())
para = [[i for i in map(int,input().split())] for j in range(M)]
graph =[[0 for i in range(N)] for  j in range(N)]
for i in range(M):
    graph[para[i][0]-1][para[i][1]-1] = 1
    graph[para[i][1]-1][para[i][0]-1] = 1 

#seen = [False]*(N)
ans = 0
for i in range(M):
    seen = [False]*(N)
    graph[para[i][0]-1][para[i][1]-1] = 0
    graph[para[i][1]-1][para[i][0]-1] = 0
    if False in check(graph,seen,0):
        ans += 1
    graph[para[i][0]-1][para[i][1]-1] = 1
    graph[para[i][1]-1][para[i][0]-1] = 1 

print(ans)

Buggy python submission (verdict: Runtime Error):
"""
一本を外して、それが非連結であるのかの判定をしていく
"""
#連結かどうかの判定
#得られている辺をたどって全ノードにたどり着けたらOK
def check(graph,seen,now):
    seen[now] = True 
    for i in range(len(graph[now])):
        if seen[i] :
            continue
        if graph[now][i] == 0 :
            continue
        check(graph,seen,i)
    return seen


#入力
N,M = map(int,input().split())
para = [[i for i in map(int,input().split())] for j in range(M)]
graph =[[0 for i in range(N)] for  j in range(M)]
for i in range(M):
    graph[para[i][0]-1][para[i][1]-1] = 1
    graph[para[i][1]-1][para[i][0]-1] = 1 

#seen = [False]*(N)
ans = 0
for i in range(M):
    seen = [False]*(N)
    graph[para[i][0]-1][para[i][1]-1] = 0
    graph[para[i][1]-1][para[i][0]-1] = 0
    if False in check(graph,seen,0):
        ans += 1
    graph[para[i][0]-1][para[i][1]-1] = 1
    graph[para[i][1]-1][para[i][0]-1] = 1 
print(ans)

Fixed submission:
def check(graph,seen,now):
    seen[now] = True 
    for i in range(len(graph[now])):
        if seen[i] :
            continue
        if graph[now][i] == 0 :
            continue
        check(graph,seen,i)
    return seen


#入力
N,M = map(int,input().split())
para = [[i for i in map(int,input().split())] for j in range(M)]
graph =[[0 for i in range(N)] for  j in range(N)]
for i in range(M):
    graph[para[i][0]-1][para[i][1]-1] = 1
    graph[para[i][1]-1][para[i][0]-1] = 1 

#seen = [False]*(N)
ans = 0
for i in range(M):
    seen = [False]*(N)
    graph[para[i][0]-1][para[i][1]-1] = 0
    graph[para[i][1]-1][para[i][0]-1] = 0
    if False in check(graph,seen,0):
        ans += 1
    graph[para[i][0]-1][para[i][1]-1] = 1
    graph[para[i][1]-1][para[i][0]-1] = 1 

print(ans)