Problem:
Score : 400 points

Problem Statement

There are N persons called Person 1 through Person N.

You are given M facts that "Person A_i and Person B_i are friends." The same fact may be given multiple times.

If X and Y are friends, and Y and Z are friends, then X and Z are also friends. There is no friendship that cannot be derived from the M given facts.

Takahashi the evil wants to divide the N persons into some number of groups so that every person has no friend in his/her group.

At least how many groups does he need to make?

Constraints

2 \leq N \leq 2\times 10^5

0 \leq M \leq 2\times 10^5

1\leq A_i,B_i\leq N

A_i \neq B_i

Input

Input is given from Standard Input in the following format:

N M
A_1 B_1
\vdots
A_M B_M

Output

Print the answer.

Sample Input 1

5 3
1 2
3 4
5 1

Sample Output 1

3

Dividing them into three groups such as \{1,3\}, \{2,4\}, and \{5\} achieves the goal.

Sample Input 2

4 10
1 2
2 1
1 2
2 1
1 2
1 3
1 4
2 3
2 4
3 4

Sample Output 2

4

Sample Input 3

10 4
3 1
4 1
5 9
2 6

Sample Output 3

3

Solution in PyPy3 (7.3.0) (judge verdict: Wrong Answer)

import sys
import os

def _S(): return sys.stdin.readline().rstrip()
def I(): return int(_S())
def LS(): return list(_S().split())
def LI(): return list(map(int,LS()))

if os.getenv("LOCAL"):
    inputFile = basename_without_ext = os.path.splitext(os.path.basename(__file__))[0]+'.txt'
    sys.stdin = open(inputFile, "r")

N,M = LI()
AB = [LI() for _ in range(M)]

if M==0:
    print(1)
    exit()

# 無向グラフ
G = []
for _ in [0]*N:
    G.append([False]*N)

for r in AB:
    f = r[0]-1
    t = r[1]-1
    G[f][t] = True
    G[t][f] = True

used = [False] * N

ss = []
for i in range(N):
    if used[i]==True:
        continue
    used[i]=True
    
    s = set([i])
    l = [i for i, x in enumerate(G[i]) if x == True and used[i]==False]
    for j in l:
        used[j]=True
        s.add(j)
        for i,x in enumerate(G[i]):
            if x == True and used[i]==False:
                s.add(i)
    ss.append(len(s))

print(max(ss))