text: columns = int(input())
  numbers_to_get = 0
  numbers_gotten = list()
  
  for x in range(1, columns+1):
      numbers_to_get += x
  
  count = 1
  counter = 0
  while counter != numbers_to_get:
      if count % 2 != 0:
          numbers_gotten.append(count)
          count += 1
      counter += 1
  
  total = 0
  for num in numbers_gotten:
      total += num
  
  print(total)
  