output_description: Print the ID numbers for all the cities, in ascending order of indices (City
  1, City 2, ...).
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N M
      P_1 Y_1
      :
      P_M Y_M
attempt: N, M = [int(a) for a in input().strip().split()]
  P = []
  Y = []
  prefs = {}
  YtoIdx = {}
  results = ["" for i in range(0, M)]
  for i in range(0, M):
      pk, yk = [int(a) for a in input().strip().split()]
      if not pk in prefs:
          prefs[pk] = []
      prefs[pk].append(yk)
      P.append(pk)
      Y.append(yk)
      YtoIdx[yk] = i
  
  for p in prefs.keys():
      prefs[p].sort()
      for i, y in enumerate(prefs[p]):
          pre = str(p).zfill(6)
          suf = str(i + 1).zfill(6)
          results[YtoIdx[y]] = pre + suf
  
  for res in results:
      print(res)
  
problem_description: Statement
  
  In Republic of Atcoder, there are N prefectures, and a total of M cities that
  belong to those prefectures.
  
  City i is established in year Y_i and belongs to Prefecture P_i.
  
  You can assume that there are no multiple cities that are established in the
  same year.
  
  It is decided to allocate a 12-digit ID number to each city.
  
  If City i is the x-th established city among the cities that belong to
  Prefecture i, the first six digits of the ID number of City i is P_i, and the
  last six digits of the ID number is x.
  
  Here, if P_i or x (or both) has less than six digits, zeros are added to the
  left until it has six digits.
  
  Find the ID numbers for all the cities.
  
  Note that there can be a prefecture with no cities.
samples: [{"input": "2 3\n    1 32\n    2 63\n    1 12", "output": "000001000002\n    000002000001\n    000001000001\n    \n\n  * As City 1 is the second established city among the cities that belong to Prefecture 1, its ID number is 000001000002.\n  * As City 2 is the first established city among the cities that belong to Prefecture 2, its ID number is 000002000001.\n  * As City 3 is the first established city among the cities that belong to Prefecture 1, its ID number is 000001000001.\n\n* * *"}, {"input": "2 3\n    2 55\n    2 77\n    2 99", "output": "000002000001\n    000002000002\n    000002000003"}]