input: Write a function to convert a positive integer to negative or vice versa using bitwise NOT operator. If the given number is zero, return zero.
  def convert_to_negative(x):
      return ~x + 1
  
  def convert_to_positive(x):
      return ~(x - 1)
  
  assert convert_to_negative(5) == -5
  assert convert_to_negative(-5) == 5
  assert convert_to_positive(5) == -5
  assert convert_to_positive(-5) == 5
  assert convert_to_negative(0) == 0
  assert convert_to_positive(0) == 0
output: def convert_to_negative(x):
      return ~x + 1 if x != 0 else 0
  
  def convert_to_positive(x):
      return ~(x - 1) if x != 0 else 0