Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque

N, M = [int(x) for x in input().split()]

friends_map = {n : set() for n in range(N)}
remain_user = set()
for m in range(M):
    a, b = [int(x) - 1 for x in input().split()]

    friends_map[a].add(b)
    friends_map[b].add(a)
    remain_user.add(a)
    remain_user.add(b)

stack = deque()
stack.appendleft(0)

max_group = 1
watch = [0] * N
count = 0
while stack:
    now = stack.popleft()

    if watch[now] == 0:
        remain_user.discard(now)
        count += 1
        watch[now] = 1

    if now in friends_map:
        for next_node in friends_map[now]:
            if watch[next_node] == 0:
                stack.appendleft(next_node)

    if not stack:
        max_group = max(count, max_group)

        if remain_user:
            stack.appendleft(remain_user.pop())
            count = 0

print(max_group)


Fixed submission:
from collections import deque

N, M = [int(x) for x in input().split()]

friends_map = {n : set() for n in range(N)}
remain_user = set()
for m in range(M):
    a, b = [int(x) - 1 for x in input().split()]

    friends_map[a].add(b)
    friends_map[b].add(a)
    remain_user.add(a)
    remain_user.add(b)

stack = deque()
stack.appendleft(0)

max_group = 1
watch = [0] * N
count = 0
while stack:
    now = stack.popleft()

    if watch[now] == 0:
        remain_user.discard(now)
        watch[now] = 1
        count += 1

        for next_node in friends_map[now]:
            if watch[next_node] == 0:
                stack.appendleft(next_node)

    if not stack:
        max_group = max(count, max_group)

        if remain_user:
            stack.appendleft(remain_user.pop())
            count = 0

print(max_group)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque

N, M = [int(x) for x in input().split()]

friends_map = {}
remain_user = set()
for m in range(M):
    a, b = [int(x) - 1 for x in input().split()]

    if a in friends_map:
        friends_map[a].add(b)
    else:
        friends_map[a] = {b}

    if b in friends_map:
        friends_map[b].add(a)
    else:
        friends_map[b] = {a}

    remain_user.add(a)
    remain_user.add(b)

stack = deque()
stack.appendleft(0)

max_group = 1
watch = [0] * N
count = 0
while stack:
    now = stack.popleft()
    remain_user.discard(now)

    if watch[now] == 0:
        count += 1
        watch[now] = 1

    if now in friends_map:
        for next_node in friends_map[now]:
            if watch[next_node] == 0:
                stack.appendleft(next_node)
                remain_user.discard(next_node)

    if not stack:
        max_group = max(count, max_group)

        if remain_user:
            stack.appendleft(remain_user.pop())
            count = 0

print(max_group)


Fixed submission:
from collections import deque

N, M = [int(x) for x in input().split()]

friends_map = {n : set() for n in range(N)}
remain_user = set()
for m in range(M):
    a, b = [int(x) - 1 for x in input().split()]

    friends_map[a].add(b)
    friends_map[b].add(a)
    remain_user.add(a)
    remain_user.add(b)

stack = deque()
stack.appendleft(0)

max_group = 1
watch = [0] * N
count = 0
while stack:
    now = stack.popleft()

    if watch[now] == 0:
        remain_user.discard(now)
        watch[now] = 1
        count += 1

        for next_node in friends_map[now]:
            if watch[next_node] == 0:
                stack.appendleft(next_node)

    if not stack:
        max_group = max(count, max_group)

        if remain_user:
            stack.appendleft(remain_user.pop())
            count = 0

print(max_group)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque

N, M = [int(x) for x in input().split()]

friends_map = {}
remain_user = set()
for m in range(M):
    a, b = [int(x) - 1 for x in input().split()]

    if a in friends_map:
        friends_map[a].add(b)
    else:
        friends_map[a] = {b}

    if b in friends_map:
        friends_map[b].add(a)
    else:
        friends_map[b] = {a}

    remain_user.add(a)
    remain_user.add(b)

stack = deque()
stack.appendleft(0)

max_group = 1
watch = set()
while stack:
    now = stack.popleft()
    remain_user.discard(now)
    watch.add(now)

    if now in friends_map:
        for next_node in friends_map[now]:
            if not next_node in watch:
                stack.appendleft(next_node)
                remain_user.discard(next_node)

    if not stack:
        if len(watch) > max_group:
            max_group = len(watch)

        if remain_user:
            stack.appendleft(remain_user.pop())
            watch = set()

print(max_group)


Fixed submission:
from collections import deque

N, M = [int(x) for x in input().split()]

friends_map = {n : set() for n in range(N)}
remain_user = set()
for m in range(M):
    a, b = [int(x) - 1 for x in input().split()]

    friends_map[a].add(b)
    friends_map[b].add(a)
    remain_user.add(a)
    remain_user.add(b)

stack = deque()
stack.appendleft(0)

max_group = 1
watch = [0] * N
count = 0
while stack:
    now = stack.popleft()

    if watch[now] == 0:
        remain_user.discard(now)
        watch[now] = 1
        count += 1

        for next_node in friends_map[now]:
            if watch[next_node] == 0:
                stack.appendleft(next_node)

    if not stack:
        max_group = max(count, max_group)

        if remain_user:
            stack.appendleft(remain_user.pop())
            count = 0

print(max_group)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque

N, M = [int(x) for x in input().split()]

friends_map = {}

for m in range(M):
    a, b = [int(x) - 1 for x in input().split()]

    if a in friends_map:
        friends_map[a].add(b)
    else:
        friends_map[a] = {b}

    if b in friends_map:
        friends_map[b].add(a)
    else:
        friends_map[b] = {a}

stack = deque()
stack.appendleft(0)

remain_user = {i for i in range(N)}

max_group = 0
watch = set()
while stack:
    now = stack.popleft()
    remain_user.discard(now)
    watch.add(now)

    if now in friends_map:
        for next_node in friends_map[now]:
            if not next_node in watch:
                stack.appendleft(next_node)
                remain_user.discard(next_node)

    if not stack:
        if len(watch) > max_group:
            max_group = len(watch)

        if remain_user:
            stack.appendleft(remain_user.pop())
            watch = set()

print(max_group)


Fixed submission:
from collections import deque

N, M = [int(x) for x in input().split()]

friends_map = {n : set() for n in range(N)}
remain_user = set()
for m in range(M):
    a, b = [int(x) - 1 for x in input().split()]

    friends_map[a].add(b)
    friends_map[b].add(a)
    remain_user.add(a)
    remain_user.add(b)

stack = deque()
stack.appendleft(0)

max_group = 1
watch = [0] * N
count = 0
while stack:
    now = stack.popleft()

    if watch[now] == 0:
        remain_user.discard(now)
        watch[now] = 1
        count += 1

        for next_node in friends_map[now]:
            if watch[next_node] == 0:
                stack.appendleft(next_node)

    if not stack:
        max_group = max(count, max_group)

        if remain_user:
            stack.appendleft(remain_user.pop())
            count = 0

print(max_group)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque

N, M = [int(x) for x in input().split()]

friends_map = {}

for m in range(M):
    a, b = [int(x) - 1 for x in input().split()]

    if a in friends_map:
        friends_map[a].add(b)
    else:
        friends_map[a] = {b}

    if b in friends_map:
        friends_map[b].add(a)
    else:
        friends_map[b] = {a}

stack = deque()
stack.appendleft(0)

remain_user = {i for i in range(N)}

max_group = 0
watch = set()
while stack:
    now = stack.popleft()
    remain_user.discard(now)
    watch.add(now)

    if now in friends_map:
        for next_node in friends_map[now]:
            if not next_node in watch:
                stack.appendleft(next_node)
                remain_user.discard(next_node)

    if len(watch) > max_group:
        max_group = len(watch)

    if not stack:
        if remain_user:
            stack.appendleft(remain_user.pop())
            watch = set()

print(max_group)


Fixed submission:
from collections import deque

N, M = [int(x) for x in input().split()]

friends_map = {n : set() for n in range(N)}
remain_user = set()
for m in range(M):
    a, b = [int(x) - 1 for x in input().split()]

    friends_map[a].add(b)
    friends_map[b].add(a)
    remain_user.add(a)
    remain_user.add(b)

stack = deque()
stack.appendleft(0)

max_group = 1
watch = [0] * N
count = 0
while stack:
    now = stack.popleft()

    if watch[now] == 0:
        remain_user.discard(now)
        watch[now] = 1
        count += 1

        for next_node in friends_map[now]:
            if watch[next_node] == 0:
                stack.appendleft(next_node)

    if not stack:
        max_group = max(count, max_group)

        if remain_user:
            stack.appendleft(remain_user.pop())
            count = 0

print(max_group)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque

N, M = [int(x) for x in input().split()]

friends_map = {}

for m in range(M):
    a, b = [int(x) - 1 for x in input().split()]

    if a in friends_map:
        friends_map[a].add(b)
    else:
        friends_map[a] = {b}

    if b in friends_map:
        friends_map[b].add(a)
    else:
        friends_map[b] = {a}

stack = deque()
stack.appendleft(0)

remain_user = {i for i in range(N)}

max_group = 0
watch = set()
while stack:
    now = stack.popleft()
    remain_user.discard(now)
    watch.add(now)

    if now in friends_map:
        for next_node in friends_map[now]:
            if not next_node in watch:
                stack.appendleft(next_node)
                remain_user.discard(next_node)

    if len(watch) > max_group:
        max_group = len(watch)

    if not stack:
        if remain_user:
            stack.appendleft(remain_user.pop())
            watch = set()

print(max_group)


Fixed submission:
from collections import deque

N, M = [int(x) for x in input().split()]

friends_map = {n : set() for n in range(N)}
remain_user = set()
for m in range(M):
    a, b = [int(x) - 1 for x in input().split()]

    friends_map[a].add(b)
    friends_map[b].add(a)
    remain_user.add(a)
    remain_user.add(b)

stack = deque()
stack.appendleft(0)

max_group = 1
watch = [0] * N
count = 0
while stack:
    now = stack.popleft()

    if watch[now] == 0:
        remain_user.discard(now)
        watch[now] = 1
        count += 1

        for next_node in friends_map[now]:
            if watch[next_node] == 0:
                stack.appendleft(next_node)

    if not stack:
        max_group = max(count, max_group)

        if remain_user:
            stack.appendleft(remain_user.pop())
            count = 0

print(max_group)