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: from collections import Counter
  
  n, m = map(int, input().split())
  if m == 0:
      print("0")
  else:
      ab = [map(int, input().split()) for _ in range(m)]
      a, b = [list(i) for i in zip(*ab)]
  
      a.extend(b)
      c = Counter(a)
      most = c.most_common(1)[0][0]
  
      temp = []
      for i in range(m):
          if a[i] == most or b[i] == most:
              if a[i] == b[i]:
                  continue
              temp.append(a[i])
              temp.append(b[i])
      temp = list(set(temp))
      print(len(temp))
  
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"}]