input: Write a function to generate the Fibonacci series up to a given number `n` and print each number in the series. The function should return the Fibonacci number at the position `n`. If `n` is less than 0, the function should print "Incorrect input" and return `None`.
  def fibonacci_series(n):
      if n < 0:
          print("Incorrect input")
          return None
      a, b = 0, 1
      series = [a]
      while b <= n:
          series.append(b)
          a, b = b, a + b
      for num in series:
          print(num)
      return series[-1] if series else None
  
  # Test cases
  assert fibonacci_series(10) is None
  assert fibonacci_series(-5) is None
  assert fibonacci_series(0) == 0
  assert fibonacci_series(1) == 1
  assert fibonacci_series(8) == 21
  assert fibonacci_series(13) == 233
output: def fibonacci_series(n):
      if n < 0:
          print("Incorrect input")
          return None
      a, b = 0, 1
      series = [a]
      while b <= n:
          series.append(b)
          a, b = b, a + b
      for num in series:
          print(num)
      return series[-1] if series else None