output_description: Print the maximum number of points you can gain.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N
      A_1 A_2 \cdots A_{3N}
attempt: # 途中まで
  N = int(input())
  A = list(map(int, input().split()))
  
  DP = [[-1] * (N + 1) for _ in range(N + 1)]
  
  R = {}
  for i in range(5):
      a = A[i]
      if a in R:
          R[a] += 1
      else:
          R[a] = 1
  
  Flag = 0
  for i in R.keys():
      if R[i] >= 3:
          Flag = 1
          R[i] -= 3
  
  L = []
  for i in R.keys():
      if R[i] == 2:
          DP[i][i] = Flag
      elif R[i] == 1:
          L.append(R[i])
  
  for i in range(len(L) - 1):
      for j in range(i + 1, len(L)):
          DP[L[i]][L[j]] = Flag
  
  print(DP)
  
  for i in range(5, N * 3, 3):
      R = {}
      for j in range(i, i + 3):
          pass
  
problem_description: Statement
  
  We have 3N cards arranged in a row from left to right, where each card has an
  integer between 1 and N (inclusive) written on it. The integer written on the
  i-th card from the left is A_i.
  
  You will do the following operation N-1 times:
  
    * Rearrange the five leftmost cards in any order you like, then remove the three leftmost cards. If the integers written on those three cards are all equal, you gain 1 point.
  
  After these N-1 operations, if the integers written on the remaining three
  cards are all equal, you will gain 1 additional point.
  
  Find the maximum number of points you can gain.
samples: [{"input": "2\n    1 2 1 2 2 1", "output": "2\n    \n\nLet us rearrange the five leftmost cards so that the integers written on the\nsix cards will be 2\\ 2\\ 2\\ 1\\ 1\\ 1 from left to right.\n\nThen, remove the three leftmost cards, all of which have the same integer 2,\ngaining 1 point.\n\nNow, the integers written on the remaining cards are 1\\ 1\\ 1.\n\nSince these three cards have the same integer 1, we gain 1 more point.\n\nIn this way, we can gain 2 points - which is the maximum possible.\n\n* * *"}, {"input": "3\n    1 1 2 2 3 3 3 2 1", "output": "1\n    \n\n* * *"}, {"input": "3\n    1 1 2 2 2 3 3 3 1", "output": "3"}]