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())
  ex = [0 for i in range(n)]
  fri = {}
  
  for i in range(m):
      a, b = map(int, input().split())
      if ex[a - 1] == 0 and ex[b - 1] == 0:
          if a > b:
              a, b = b, a
          ex[a - 1] = a
          ex[b - 1] = a
          fri[a] = [a, b]
      elif ex[a - 1] == 0:
          ex[a - 1] = ex[b - 1]
          fri[ex[b - 1]].append(a)
      elif ex[b - 1] == 0:
          ex[b - 1] = ex[a - 1]
          fri[ex[a - 1]].append(b)
      elif ex[a - 1] == ex[b - 1]:
          continue
      else:
          shozoku = min(ex[a - 1], ex[b - 1])
          mu = max(ex[a - 1], ex[b - 1])
          for j in range(len(fri[mu])):
              ex[fri[mu][j] - 1] = shozoku
          fri[shozoku].extend(fri.pop(mu))
  
  ans = 0
  for key in fri:
      ans = max(ans, len(fri[key]))
  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"}]