output_description: When the minimum required number of recorders is x, print the value of x.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N C
      s_1 t_1 c_1
      :
      s_N t_N c_N
attempt: n, c = map(int, input().split(" "))
  
  time = list()
  for i in range(0, n):
      s, t, c = map(int, input().split(" "))
      time.append((s, t, c))
  
  time_sorted = sorted(time, key=lambda x: (x[2], x[1]))
  
  time_joined = list()
  prev = None
  for current in time_sorted:
      if prev is None:
          prev = current
  
      elif prev[2] == current[2] and prev[1] == current[0]:
          prev = (prev[0], current[1], current[2])
  
      else:
          time_joined.append(prev)
          prev = current
  
  # time_joined.append(prev)
  print(time_joined)
  
  time_list = list()
  for s, t, c in time_joined:
      time_list.append((s - 0.5, "s"))
      time_list.append((t, "t"))
  
  time_list_sorted = sorted(time_list, key=lambda x: x[0])
  
  current = 0
  ans = 0
  
  for t, s in time_list_sorted:
      if s == "s":
          current += 1
          ans = max(ans, current)
      else:
          current -= 1
  
  print(ans)
  
problem_description: Statement
  
  Joisino is planning to record N TV programs with recorders.
  
  The TV can receive C channels numbered 1 through C.
  
  The i-th program that she wants to record will be broadcast from time s_i to
  time t_i (including time s_i but not t_i) on Channel c_i.
  
  Here, there will never be more than one program that are broadcast on the same
  channel at the same time.
  
  When the recorder is recording a channel from time S to time T (including time
  S but not T), it cannot record other channels from time S-0.5 to time T
  (including time S-0.5 but not T).
  
  Find the minimum number of recorders required to record the channels so that
  all the N programs are completely recorded.
samples: [{"input": "3 2\n    1 7 2\n    7 8 1\n    8 12 1", "output": "2\n    \n\nTwo recorders can record all the programs, for example, as follows:\n\n  * With the first recorder, record Channel 2 from time 1 to time 7. The first program will be recorded. Note that this recorder will be unable to record other channels from time 0.5 to time 7.\n  * With the second recorder, record Channel 1 from time 7 to time 12. The second and third programs will be recorded. Note that this recorder will be unable to record other channels from time 6.5 to time 12.\n\n* * *"}, {"input": "3 4\n    1 3 2\n    3 4 4\n    1 4 3", "output": "3\n    \n\nThere may be a channel where there is no program to record.\n\n* * *"}, {"input": "9 4\n    56 60 4\n    33 37 2\n    89 90 3\n    32 43 1\n    67 68 3\n    49 51 3\n    31 32 3\n    70 71 1\n    11 12 3", "output": "2"}]