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())
  l = [list() for _ in range(c + 1)]
  for _ in range(n):
      s, t, ch = map(int, input().split())
      l[ch].append((s, t))
  al = list()
  for x in l:
      x.sort()
  for i in range(c + 1):
      if l[i] == []:
          continue
      t = list()
      for j in range(len(l[i]) - 1):
          if l[i][j][1] == l[i][j + 1][0]:
              l[i][j + 1] = (l[i][j][0], l[i][j + 1][1])
          else:
              t.append(l[i][j])
      t.append(l[i][-1])
      al += t
  tl = [0] * (10**5 + 10)
  for s, t in al:
      tl[s] += 1
      tl[t + 1] -= 1
  for i in range(10**5 + 9):
      tl[i + 1] += tl[i]
  print(max(tl))
  
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"}]