output_description: Print the maximum total reward that you can earn no later than M days from
  today.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N M
      A_1 B_1
      A_2 B_2
      \vdots
      A_N B_N
attempt: IN1 = input()
  N, M = [int(x) for x in IN1.split()]
  
  IN2 = [[int(x) for x in input().split()] for _ in range(N)]
  # 戦略 残りj日のとき働くべき：j日より期限が短く、最大の報酬が得られるもの
  j = 1
  E = 0
  while j < M + 1:
      j_choices = [x for x in IN2 if x[0] <= j]
      # print(j_choices)
      # print(len(j_choices))
      if len(j_choices) > 1:
          M = max([x[1] for x in j_choices])
          j_choices = [x for x in j_choices if x[1] == M]
          m = min([x[0] for x in j_choices])
          j_choice = [x for x in j_choices if x[0] == m][0]
          E = E + j_choice[1]
          IN2.remove(j_choice)
      elif len(j_choices) == 1:
          j_choice = j_choices[0]
          # print(j_choice)
          E = E + j_choice[1]
          IN2.remove(j_choice)
      j += 1
  print(E)
  
problem_description: Statement
  
  There are N one-off jobs available. If you take the i-th job and complete it,
  you will earn the reward of B_i after A_i days from the day you do it.
  
  You can take and complete at most one of these jobs in a day.
  
  However, you cannot retake a job that you have already done.
  
  Find the maximum total reward that you can earn no later than M days from
  today.
  
  You can already start working today.
samples: [{"input": "3 4\n    4 3\n    4 1\n    2 2", "output": "5\n    \n\nYou can earn the total reward of 5 by taking the jobs as follows:\n\n  * Take and complete the first job today. You will earn the reward of 3 after four days from today.\n  * Take and complete the third job tomorrow. You will earn the reward of 2 after two days from tomorrow, that is, after three days from today.\n\n* * *"}, {"input": "5 3\n    1 2\n    1 3\n    1 4\n    2 1\n    2 3", "output": "10\n    \n\n* * *"}, {"input": "1 1\n    2 1", "output": "0"}]