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: a, b, d = list(map(int, input().split())), [], 0
  n, m = a[0], a[1]
  for i in range(n):
      b.append(list(map(int, input().split())))
  b.sort(key=lambda x: (x[0], x[1]))
  for i in range(m):
      c = []
      for j in range(len(b)):
          if m - i >= b[j][0]:
              c.append(b[j])
      c = sorted(c, key=lambda x: x[1])
      if len(c) < 1:
          break
      else:
          d += c[-1][1]
          b.remove(c[-1])
  print(d)
  
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"}]