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())
  tf_dict = {}
  for i, n in enumerate(range(N)):
      A = int(input())
      tmp_dict = {}
      for a in range(A):
          xy = input().split()
          tmp_dict[int(xy[0])] = int(xy[1])
      tf_dict[i + 1] = tmp_dict
  
  True_set = set()
  False_set = set()
  for key in tf_dict.keys():
      for item in tf_dict[key].items():
          if item[1] == 1:
              if (item[0] not in True_set) & (item[0] not in False_set):
                  True_set.add(item[0])
                  True_set.add(key)
              elif item[0] in True_set:
                  True_set.add(key)
              elif item[0] in False_set:
                  False_set.add(key)
          if item[1] == 0:
              if (item[0] not in True_set) & (item[0] not in False_set):
                  False_set.add(item[0])
                  True_set.add(key)
              elif item[0] in True_set:
                  False_set.add(key)
              elif item[0] in False_set:
                  True_set.add(key)
  
  if len(False_set & True_set) != 0:
      print("0")
  else:
      print(len(True_set))
  
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"}]