input: Write a function to convert a positive integer to negative or vice versa using bitwise NOT operator.
  
  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
output: def convert_to_negative(x): 
      return ~x + 1 
    
  def convert_to_positive(x): 
      return ~(x-1)