input: Write a function to check the temperature and print appropriate messages.
  assert check_temperature(10) == 'It is below 15 degrees.'
  assert check_temperature(20) == 'Temperature is normal.'
  assert check_temperature(35) == 'It is over 30 degrees.'
output: def check_temperature(temp):
      if temp < 15:
          return 'It is below 15 degrees.'
      elif temp > 30:
          return 'It is over 30 degrees.'
      else:
          return 'Temperature is normal.'