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: # abc177_D_2_特定のnが特定のlistに含まれることを確認するまで、iter
  int_n, int_m = map(int, input().split())
  list_agg = list()
  for i in range(int_m):
      list_tmp = list(map(int, input().split()))
      list_agg.append(list_tmp)
  
  
  def get_unique_list(seq):
      seen = []
      return [x for x in seq if x not in seen and not seen.append(x)]
  
  
  flag = 100
  list_agg_tmp = list_agg
  while flag <= 1:
      list_set_agg = list()
      flag = 0
      for iter_n in range(1, int_n + 1):
          list_tmp_add = list()
          n_flag = 0
          for i_list in list_agg_tmp:
              if iter_n in i_list:
                  list_tmp_add = list_tmp_add + i_list
                  n_flag = n_flag + 1
          if n_flag > flag:
              flag = n_flag
          list_set_agg.append(list(set(list_tmp_add)))
      list_agg_tmp = get_unique_list(list_set_agg)
  
  int_max_len = 0
  for i in list_agg_tmp:
      if len(i) > int_max_len:
          int_max_len = len(i)
  
  print(int_max_len)
  
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"}]