Buggy python submission (verdict: Runtime Error):
import os
import sys
from io import BytesIO, IOBase

BUFSIZE = 8192
class FastIO(IOBase):
    newlines = 0

    def __init__(self, file):
        self._fd = file.fileno()
        self.buffer = BytesIO()
        self.writable = "x" in file.mode or "r" not in file.mode
        self.write = self.buffer.write if self.writable else None

    def read(self):
        while True:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            if not b:
                break
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines = 0
        return self.buffer.read()

    def readline(self):
        while self.newlines == 0:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            self.newlines = b.count(b"\n") + (not b)
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines -= 1
        return self.buffer.readline()

    def flush(self):
        if self.writable:
            os.write(self._fd, self.buffer.getvalue())
            self.buffer.truncate(0), self.buffer.seek(0)
class IOWrapper(IOBase):
    def __init__(self, file):
        self.buffer = FastIO(file)
        self.flush = self.buffer.flush
        self.writable = self.buffer.writable
        self.write = lambda s: self.buffer.write(s.encode("ascii"))
        self.read = lambda: self.buffer.read().decode("ascii")
        self.readline = lambda: self.buffer.readline().decode("ascii")
sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)
input = lambda: sys.stdin.readline().rstrip("\r\n")

def list2d(a, b, c): return [[c] * b for i in range(a)]
def list3d(a, b, c, d): return [[[d] * c for j in range(b)] for i in range(a)]
def list4d(a, b, c, d, e): return [[[[e] * d for j in range(c)] for j in range(b)] for i in range(a)]
def ceil(x, y=1): return int(-(-x // y))
def Yes(): print('Yes')
def No(): print('No')
def YES(): print('YES')
def NO(): print('NO')
INF = 10 ** 18
MOD = 10**9+7

from math import gcd

Ri = lambda : [int(x) for x in sys.stdin.readline().split()]
ri = lambda : sys.stdin.readline().strip()

n,m = Ri()
par = [i for i in range(n)]
val = [1 for i in range(n)]

def find(chi):
    if par[chi] == chi:
        return chi
    temp = find(par[chi])
    par[chi] = temp
    return temp

def union(a,b):
    pa,pb = find(a),find(b)
    par[pb] = pa
    val[pa]+=val[pb]

ncc= n
for i in range(m):
    a,b = Ri();a-=1;b-=1
    pa,pb = find(a),find(b)
    if pa != pb:
        ncc-=1
        union(a,b)

lis = []
se = set()
for i in range(n):
    p = find(i)
    if p not in se:
        se.add(p)
        lis.append(val[p])
lis.sort()
ans = 0
summ = 0
for i in range(len(lis)):
    val = (lis[i]-summ)
    ans+=val
    summ+=val
print(ans)


Fixed submission:
import os
import sys
from io import BytesIO, IOBase

BUFSIZE = 8192
class FastIO(IOBase):
    newlines = 0

    def __init__(self, file):
        self._fd = file.fileno()
        self.buffer = BytesIO()
        self.writable = "x" in file.mode or "r" not in file.mode
        self.write = self.buffer.write if self.writable else None

    def read(self):
        while True:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            if not b:
                break
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines = 0
        return self.buffer.read()

    def readline(self):
        while self.newlines == 0:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            self.newlines = b.count(b"\n") + (not b)
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines -= 1
        return self.buffer.readline()

    def flush(self):
        if self.writable:
            os.write(self._fd, self.buffer.getvalue())
            self.buffer.truncate(0), self.buffer.seek(0)
class IOWrapper(IOBase):
    def __init__(self, file):
        self.buffer = FastIO(file)
        self.flush = self.buffer.flush
        self.writable = self.buffer.writable
        self.write = lambda s: self.buffer.write(s.encode("ascii"))
        self.read = lambda: self.buffer.read().decode("ascii")
        self.readline = lambda: self.buffer.readline().decode("ascii")
sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)
input = lambda: sys.stdin.readline().rstrip("\r\n")

def list2d(a, b, c): return [[c] * b for i in range(a)]
def list3d(a, b, c, d): return [[[d] * c for j in range(b)] for i in range(a)]
def list4d(a, b, c, d, e): return [[[[e] * d for j in range(c)] for j in range(b)] for i in range(a)]
def ceil(x, y=1): return int(-(-x // y))
def Yes(): print('Yes')
def No(): print('No')
def YES(): print('YES')
def NO(): print('NO')
INF = 10 ** 18
MOD = 10**9+7

from math import gcd

from types import GeneratorType
def bootstrap(func, stack=[]):
    def wrapped_function(*args, **kwargs):
        if stack:
            return func(*args, **kwargs)
        else:
            call = func(*args, **kwargs)
            while True:
                if type(call) is GeneratorType:
                    stack.append(call)
                    call = next(call)
                else:
                    stack.pop()
                    if not stack:
                        break
                    call = stack[-1].send(call)
            return call
 
    return wrapped_function

Ri = lambda : [int(x) for x in sys.stdin.readline().split()]
ri = lambda : sys.stdin.readline().strip()

n,m = Ri()
par = [i for i in range(n)]
val = [1 for i in range(n)]

@bootstrap
def find(chi):
    if par[chi] == chi:
        yield chi
    temp = yield find(par[chi])
    par[chi] = temp
    yield temp

def union(a,b):
    pa,pb = find(a),find(b)
    par[pb] = pa
    val[pa]+=val[pb]

ncc= n
for i in range(m):
    a,b = Ri();a-=1;b-=1
    pa,pb = find(a),find(b)
    if pa != pb:
        ncc-=1
        union(a,b)

lis = []
se = set()
for i in range(n):
    p = find(i)
    if p not in se:
        se.add(p)
        lis.append(val[p])
lis.sort()
ans = 0
summ = 0
for i in range(len(lis)):
    val = (lis[i]-summ)
    ans+=val
    summ+=val
print(ans)