Buggy python submission (verdict: Time Limit Exceeded):
import sys
sys.setrecursionlimit(10 ** 9)

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]

    def union(self, x, y):

        x = self.find(x)
        y = self.find(y)

        if x == y:
            return

        self.parents[x] += self.parents[y]
        self.parents[y] = x

    def size(self, x):
        return -self.parents[self.find(x)]


N, M = map(int, input().split()) 
union_find = UnionFind(N)
for _ in range(M):
    A, B = map(int, input().split())
    A -= 1
    B -= 1
    union_find.union(A, B)

answer = 0
for i in range(N):
    answer = max(answer, union_find.size(i))

print(answer)


Fixed submission:
n, m = map(int, input().split())

root = [-1]*n
def r(x):
    if root[x] < 0:
        return x
    else:
        root[x] = r(root[x])
        return root[x]

def unite(x, y):
    x = r(x)
    y = r(y)
    if x == y:
        return
    root[x] += root[y]
    root[y] = x

for i in range(m):
    a, b = map(int, input().split())
    a -= 1
    b -= 1
    unite(a, b)

ans = 0
for i in range(n):
    ans = max(ans, -root[i])

print(ans)

Buggy python submission (verdict: Runtime Error):
class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]

    def union(self, x, y):

        x = self.find(x)
        y = self.find(y)

        if x == y:
            return

        self.parents[x] += self.parents[y]
        self.parents[y] = x

    def size(self, x):
        return -self.parents[self.find(x)]


N, M = map(int, input().split()) 
union_find = UnionFind(N)
for _ in range(M):
    A, B = map(int, input().split())
    A -= 1
    B -= 1
    union_find.union(A, B)

answer = 0
for i in range(N):
    answer = max(answer, union_find.size(i))

print(answer)

Fixed submission:
n, m = map(int, input().split())

root = [-1]*n
def r(x):
    if root[x] < 0:
        return x
    else:
        root[x] = r(root[x])
        return root[x]

def unite(x, y):
    x = r(x)
    y = r(y)
    if x == y:
        return
    root[x] += root[y]
    root[y] = x

for i in range(m):
    a, b = map(int, input().split())
    a -= 1
    b -= 1
    unite(a, b)

ans = 0
for i in range(n):
    ans = max(ans, -root[i])

print(ans)

Buggy python submission (verdict: Runtime Error):
import sys
sys.setrecursionlimit(10 ** 9)

class Union_Find:
    def __init__(self, n):
        self.root = [-1]*n
    
    def find(self, x):
        if self.root[x] < 0:
            return x
        else:
            self.root[x] = self.find(self.root[x])
            return root[x]

    def unite(self, x, y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return
        else:
            self.root[x] += self.root[y]
            self.root[y] = x

    def same(self, x, y):
        return self.find(x) == self.find(y)


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

for i in range(m):
    a, b = map(int, input().split())
    a -= 1
    b -= 1
    uf.unite(a, b)

ans = 0
for i in range(n):
    size = uf.root[i]*(-1)
    ans = max(ans, size)

print(ans)

Fixed submission:
n, m = map(int, input().split())

root = [-1]*n
def r(x):
    if root[x] < 0:
        return x
    else:
        root[x] = r(root[x])
        return root[x]

def unite(x, y):
    x = r(x)
    y = r(y)
    if x == y:
        return
    root[x] += root[y]
    root[y] = x

for i in range(m):
    a, b = map(int, input().split())
    a -= 1
    b -= 1
    unite(a, b)

ans = 0
for i in range(n):
    ans = max(ans, -root[i])

print(ans)

Buggy python submission (verdict: Runtime Error):
import sys
sys.setrecursionlimit(10 ** 9)

class Union_Find:
    def __init__(self, n):
        self.root = [-1]*n
    
    def find(self, x):
        if self.root[x] < -1:
            return x
        else:
            self.root[x] = self.find(self.root[x])
            return root[x]

    def unite(self, x, y):
        x = find(x)
        y = find(y)
        if x == y:
            return
        else:
            self.root[x] += self.root[y]
            self.root[y] = x

    def same(self, x, y):
        return self.find(x) == self.find(y)


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

for i in range(m):
    a, b = map(int, input().split())
    a -= 1
    b -= 1
    uf.unite(a, b)

ans = 0
for i in range(n):
    size = uf.root[i]*(-1)
    ans = max(ans, size)

print(ans)

Fixed submission:
n, m = map(int, input().split())

root = [-1]*n
def r(x):
    if root[x] < 0:
        return x
    else:
        root[x] = r(root[x])
        return root[x]

def unite(x, y):
    x = r(x)
    y = r(y)
    if x == y:
        return
    root[x] += root[y]
    root[y] = x

for i in range(m):
    a, b = map(int, input().split())
    a -= 1
    b -= 1
    unite(a, b)

ans = 0
for i in range(n):
    ans = max(ans, -root[i])

print(ans)

Buggy python submission (verdict: Runtime Error):
class Union_Find:
    def __init__(self, n):
        self.root = [-1]*n
    
    def find(self, x):
        if self.root[x] < -1:
            return x
        else:
            self.root[x] = self.find(self.root[x])
            return root[x]

    def unite(self, x, y):
        x = find(x)
        y = find(y)
        if x == y:
            return
        else:
            self.root[x] += self.root[y]
            self.root[y] = x

    def same(self, x, y):
        return self.find(x) == self.find(y)


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

for i in range(m):
    a, b = map(int, input().split())
    a -= 1
    b -= 1
    uf.unite(a, b)

ans = 0
for i in range(n):
    size = uf.root[i]*(-1)
    ans = max(ans, size)

print(ans)

Fixed submission:
n, m = map(int, input().split())

root = [-1]*n
def r(x):
    if root[x] < 0:
        return x
    else:
        root[x] = r(root[x])
        return root[x]

def unite(x, y):
    x = r(x)
    y = r(y)
    if x == y:
        return
    root[x] += root[y]
    root[y] = x

for i in range(m):
    a, b = map(int, input().split())
    a -= 1
    b -= 1
    unite(a, b)

ans = 0
for i in range(n):
    ans = max(ans, -root[i])

print(ans)