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: import collections 
  def connected(adj,v,visited,f):
      visited[v]=True 
      f.append(v) 
      for i in adj[v]:
          if not visited[i]:
              connected(adj,i,visited,f) 
  adj=collections.defaultdict(int) 
  n,m=map(int,input().split()) 
  f={} 
  for i in range(m):
      u,v=map(int,input().split()) 
      if u<=v:f[(u,v)]=1  
      else:f[(v,u)]=1 
  for x in f:
      adj[x[0]]+=1 
      adj[x[1]]+=1 
  #print(adj) 
  print(max(list(adj.values()))+1)
  
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"}]