input: Write a function to convert a positive integer to negative or vice versa using bitwise NOT operator.
  
  ### Input:
  def convert_to_negative(x): 
      return ~x + 1 
    
  def convert_to_positive(x): 
      return ~(x-1)
  
  ### Output:
  assert convert_to_negative(5)==-5
  assert convert_to_positive(-5)==5
  assert convert_to_negative(0) == 0
  assert convert_to_positive(0) == 0
  assert convert_to_negative(100)==-100
  assert convert_to_positive(-100)==100
output: def convert_to_negative(x): 
      return ~x + 1 
    
  def convert_to_positive(x): 
      return ~(x-1)