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))