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 numpy as np
  N,M=map(int,input().split())
  mat=np.zeros((N,N))
  for _ in range(M):
      a,b=map(int,input().split())
      mat[a-1][b-1]=1
      mat[b-1][a-1]=1
  mat2=[[j for j in i] for i in mat]
  for i in range(N-1):
      for j in range(i+1,N):
          for k in range(j+1,N):
              if (mat[i][j]==1)&(mat[i][k]==1):
                  mat[j][k]=1
                  mat[k][j]=1
  print(str(int(np.max(np.sum(mat,axis=1))+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"}]