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: A, B, C, D = (int(i) for i in input().split())
  if D > B and A > C:
      E = C - (D - B)
      F = D - (A - C)
      G = A - (D - B)
      H = B - (A - C)
      print(E, F, G, H)
  elif A > C and B > D:
      E = C + (B - D)
      F = D - (A - C)
      G = A + (B - D)
      H = B - (A - C)
      print(E, F, G, H)
  elif B > D and C > A:
      E = C + (B - D)
      F = D + (C - A)
      G = A + (B - D)
      H = B + (C - A)
      print(E, F, G, H)
  else:
      E = C - (D - B)
      F = D + (C - A)
      G = A - (D - B)
      H = B + (C - A)
      print(E, F, G, H)
  
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"}]