input: Write a function to classify numbers as "positive", "negative", or "zero".
  assert classify(10) == "positive"
  assert classify(-5) == "negative"
  assert classify(0) == "zero"
  assert classify(12345) == "positive"
  assert classify(-98765) == "negative"
output: def classify(number):
      if number > 0:
          return "positive"
      elif number < 0:
          return "negative"
      else:
          return "zero"