input: Write a function to generate and print the Fibonacci series up to a given number `n`.
  
  def fibonacci(n):
      a, b = 0, 1
      if n < 0:
          print("Incorrect input")
      else:
          while a <= n:
              print(a, end=" ")
              a, b = b, a + b
  
  n = int(input("Enter a number: "))
  if n >= 0:
      fibonacci(n)
  else:
      print("Incorrect input")
  
  assert fibonacci(5) == None
  assert fibonacci(10) == None
  assert fibonacci(1) == None
  assert fibonacci(0) == None
  assert fibonacci(-1) == "Incorrect input"
output: def fibonacci(n):
      a, b = 0, 1
      if n < 0:
          print("Incorrect input")
      else:
          while a <= n:
              print(a, end=" ")
              a, b = b, a + b