output_description: Print the maximum possible number of honest persons among the N people.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N
      A_1
      x_{11} y_{11}
      x_{12} y_{12}
      :
      x_{1A_1} y_{1A_1}
      A_2
      x_{21} y_{21}
      x_{22} y_{22}
      :
      x_{2A_2} y_{2A_2}
      :
      A_N
      x_{N1} y_{N1}
      x_{N2} y_{N2}
      :
      x_{NA_N} y_{NA_N}
attempt: N = int(input())
  # A = []
  lst = [list(f"{i:0{N}b}") for i in range(2**N)]
  # X = [[] for i in range(N)]
  # Y = [[] for i in range(N)]
  
  # for i in range(N):
  #     tmp_A = int(input())
  #     A.append(tmp_A)
  #     for j in range(tmp_A):
  #         tmp_x,tmp_y = input().split()
  #         X[i].append(int(tmp_x)-1)
  #         Y[i].append(tmp_y)
  
  ans = -1
  
  # for i in range(2**N):
  #     flag = 1
  #     for j in range(N):
  #         if lst[i][j] == "1":
  #             for k in range(A[j]):
  #                if lst[i][X[j][k]] != Y[j][k]:
  #                    flag = 0
  #     if flag:
  #         tmp = 0
  #         for j in lst[i]:
  #             if j == "1":
  #                tmp += 1
  #         if tmp > ans:
  #             ans = tmp
  
  print(ans)
  
problem_description: Statement
  
  There are N people numbered 1 to N. Each of them is either an _honest_ person
  whose testimonies are always correct or an _unkind_ person whose testimonies
  may be correct or not.
  
  Person i gives A_i testimonies. The j-th testimony by Person i is represented
  by two integers x_{ij} and y_{ij}. If y_{ij} = 1, the testimony says Person
  x_{ij} is honest; if y_{ij} = 0, it says Person x_{ij} is unkind.
  
  How many honest persons can be among those N people at most?
samples: [{"input": "3\n    1\n    2 1\n    1\n    1 1\n    1\n    2 0", "output": "2\n    \n\nIf Person 1 and Person 2 are honest and Person 3 is unkind, we have two honest\npersons without inconsistencies, which is the maximum possible number of\nhonest persons.\n\n* * *"}, {"input": "3\n    2\n    2 1\n    3 0\n    2\n    3 1\n    1 0\n    2\n    1 1\n    2 0", "output": "0\n    \n\nAssuming that one or more of them are honest immediately leads to a\ncontradiction.\n\n* * *"}, {"input": "2\n    1\n    2 0\n    1\n    1 0", "output": "1"}]