output_description: Print the number of ways to choose a pair of an even number and an odd number
  from the positive integers between 1 and K (inclusive).
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      K
attempt: l = map(int, input().split())
  a = list(l)
  x1 = a[0]
  y1 = a[1]
  x2 = a[2]
  y2 = a[3]
  x = x2 - x1
  y = y2 - y1
  x3 = x2 - y
  y3 = y2 + x
  x4 = x1 - y
  y4 = y1 + x
  c = [x3, y3, x4, y4]
  print(c[0], c[1], c[2], c[3])
  
problem_description: Statement
  
  Find the number of ways to choose a pair of an even number and an odd number
  from the positive integers between 1 and K (inclusive). The order does not
  matter.
samples: [{"input": "3", "output": "2\n    \n\nTwo pairs can be chosen: (2,1) and (2,3).\n\n* * *"}, {"input": "6", "output": "9\n    \n\n* * *"}, {"input": "11", "output": "30\n    \n\n* * *"}, {"input": "50", "output": "625"}]