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

    def find(self, x):
        if self.parents[x] < x:
            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
        
        if self.parents[x] > self.parents[y]:
            x, y = y, x
            
        self.parents[x] += self.parents[y]
        self.parents[y] = x
    
    def roots(self):
        return [i for i,x in enumerate(self.parents) if x < 0]

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

uf = UnionFind(n)

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

cnt = []
for i in uf.roots():
    cnt.append(i)
    
print(max(cnt))

Fixed submission:
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
        
        if self.parents[x] > self.parents[y]:
            x,y = y,x
            
        self.parents[x] += self.parents[y]
        self.parents[y] = x

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

uf = UnionFind(n)

ab = [tuple(map(int,input().split())) for _ in range(m)]

for a,b in ab:
    uf.union(a-1,b-1)

ans = -1
for i in uf.parents:
    ans = min(i,ans)
    
print(-ans)

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

    def find(self, x):
        if self.parents[x] < x:
            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
        
        if self.parents[x] > self.parents[y]:
            x, y = y, x
            
        self.parents[x] += self.parents[y]
        self.parents[y] = x

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

uf = UnionFind(n)

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

print(abs(min(uf.parents)))

Fixed submission:
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
        
        if self.parents[x] > self.parents[y]:
            x,y = y,x
            
        self.parents[x] += self.parents[y]
        self.parents[y] = x

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

uf = UnionFind(n)

ab = [tuple(map(int,input().split())) for _ in range(m)]

for a,b in ab:
    uf.union(a-1,b-1)

ans = -1
for i in uf.parents:
    ans = min(i,ans)
    
print(-ans)