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: n, d = list(map(int, input().split(" ")))
  
  ws = []
  for _ in range(n):
      l, r = list(map(int, input().split(" ")))
      if l <= d:
          ws.append((l, r))
  
  wn = len(ws)
  
  got = 0
  chosen = []
  for i in range(d):
      j = d - i
      candi_k = 0
      candi_r = 0
      candi_t = 0
      for k, (t, r) in enumerate(wn):
          if t <= j and candi_t <= t and candi_r <= r and not k in chosen:
              candi_k = k
              candi_r = r
              candi_t = t
      chosen.append(candi_k)
      got += candi_r
  
  print(got)
  
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"}]