output_description: Print the answer.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N M
      A_1 B_1
      \vdots
      A_M B_M
attempt: n,m=map(int,input().split())
  ab=[list(map(int,input().split())) for i in range(m)]
  f=[[] for i in range(n)]
  j=1
  shozoku=[0]*n
  for i in range(m):
      if shozoku[ab[i][0]-1]==0:
          if shozoku[ab[i][1]-1]==0:
              shozoku[ab[i][0]-1]+=j
              shozoku[ab[i][1]-1]+=j
              f[j-1].append(ab[i][0])
              f[j-1].append(ab[i][1])
              j+=1
          else:
              shozoku[ab[i][0]-1]+=shozoku[ab[i][1]-1]
              f[shozoku[ab[i][1]-1]-1].append(ab[i][0])
      else:
          if shozoku[ab[i][1]-1]==0:
              shozoku[ab[i][1]-1]+=shozoku[ab[i][0]-1]
              f[shozoku[ab[i][0]-1]-1].append(ab[i][1])
          else:
            if shozoku[ab[i][1]-1]!=shozoku[ab[i][0]-1]:
              f[shozoku[ab[i][0]-1]-1].extend(f[shozoku[ab[i][1]-1]-1])
              f[shozoku[ab[i][1]-1]-1]=f[shozoku[ab[i][0]-1]-1]
  ans=1
  for i in range(n):
      ans=max(len(f[i]),ans)
  print(ans)
problem_description: 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?
samples: [{"input": "5 3\n    1 2\n    3 4\n    5 1", "output": "3\n    \n\nDividing them into three groups such as \\\\{1,3\\\\}, \\\\{2,4\\\\}, and \\\\{5\\\\}\nachieves the goal.\n\n* * *"}, {"input": "4 10\n    1 2\n    2 1\n    1 2\n    2 1\n    1 2\n    1 3\n    1 4\n    2 3\n    2 4\n    3 4", "output": "4\n    \n\n* * *"}, {"input": "10 4\n    3 1\n    4 1\n    5 9\n    2 6", "output": "3"}]