def alternateSum(n):
  positiveNumbers = [num**2 for num in [i for i in range(1,n+1) if i % 2 != 0]]
  negativeNumbers = [-num**2 for num in [i for i in range(1,n+1) if i % 2 == 0]]
  return sum(positiveNumbers + negativeNumbers)

if __name__ == "__main__":
  n = int(input('n: '))
  print(alternateSum(n))