output_description: Print the maximum number of robots that we can keep.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N
      X_1 L_1
      X_2 L_2
      \vdots
      X_N L_N
attempt: N = int(input())
  List = [list(map(int, input().split())) for i in range(N)]
  List.sort()
  
  cnt = 0
  for i in range(len(List) - 2):
      migi = int(List[i - cnt][0] + List[i - cnt][1])
      hidari = int(List[i + 2 - cnt][0] - List[i + 2 - cnt][1])
      if migi > hidari:
          List.pop(i - cnt)
          cnt = cnt + 1
  
  cnt = 0
  for i in range(len(List) - 2):
      if i > 1:
          migi = int(List[i - 2 - cnt][0] + List[i - 2 - cnt][1])
          hidari = int(List[i - cnt][0] - List[i - cnt][1])
          if migi > hidari:
              List.pop(i - cnt)
              cnt = cnt + 1
  
  cnt = 0
  for i in range(len(List) - 1):
      if i > 0:
          hidari_1 = int(List[i - cnt][0] - List[i - cnt][1])
          migi_1 = int(List[i - 1 - cnt][0] + List[i - 1 - cnt][1])
  
          migi_2 = int(List[i - cnt][0] + List[i - cnt][1])
          hidari_2 = int(List[i + 1 - cnt][0] - List[i + 1 - cnt][1])
  
          if hidari_1 < migi_1 and migi_2 > hidari_2:
              List.pop(i - cnt)
              cnt = cnt + 1
  
  cnt = 0
  for i in range(len(List) - 1):
      hidari = int(List[i + 1 - cnt][0] - List[i + 1 - cnt][1])
      migi = int(List[i - cnt][0] + List[i - cnt][1])
      if hidari < migi:
          List.pop(i - cnt)
          cnt = cnt + 1
  
  length = len(List)
  print(length)
  
problem_description: Statement
  
  In a factory, there are N robots placed on a number line. Robot i is placed at
  coordinate X_i and can extend its arms of length L_i in both directions,
  positive and negative.
  
  We want to remove zero or more robots so that the movable ranges of arms of no
  two remaining robots intersect. Here, for each i (1 \leq i \leq N), the
  movable range of arms of Robot i is the part of the number line between the
  coordinates X_i - L_i and X_i + L_i, excluding the endpoints.
  
  Find the maximum number of robots that we can keep.
samples: [{"input": "4\n    2 4\n    4 3\n    9 3\n    100 5", "output": "3\n    \n\nBy removing Robot 2, we can keep the other three robots.\n\n* * *"}, {"input": "2\n    8 20\n    1 10", "output": "1\n    \n\n* * *"}, {"input": "5\n    10 1\n    2 1\n    4 1\n    6 1\n    8 1", "output": "5"}]