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(10)==-10
  assert convert_to_positive(-10)==10
  assert convert_to_negative(0)==-1
  assert convert_to_positive(-1)==0
output: def convert_to_negative(x): 
      return ~x + 1 
    
  def convert_to_positive(x): 
      return ~(x-1)