output_description: If the depth of the snow cover is x meters, print x as an integer.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      a b
attempt: # coding:utf-8
  a, b= map(int, input().split())
  
  diff = b-a
  d = 0
  for i in enumerate(diff+1, 1):
      d += i 
  
  print(abs(d-a)
      
  
problem_description: Statement
  
  In some village, there are 999 towers that are
  1,(1+2),(1+2+3),...,(1+2+3+...+999) meters high from west to east, at
  intervals of 1 meter.
  
  It had been snowing for a while before it finally stopped. For some two
  adjacent towers located 1 meter apart, we measured the lengths of the parts of
  those towers that are not covered with snow, and the results are a meters for
  the west tower, and b meters for the east tower.
  
  Assuming that the depth of snow cover and the altitude are the same everywhere
  in the village, find the amount of the snow cover.
  
  Assume also that the depth of the snow cover is always at least 1 meter.
samples: [{"input": "8 13", "output": "2\n    \n\nThe heights of the two towers are 10 meters and 15 meters, respectively. Thus,\nwe can see that the depth of the snow cover is 2 meters.\n\n* * *"}, {"input": "54 65", "output": "1"}]