input: Write a function named `convert_using_bitwise_not` that takes a positive or negative integer as input and converts it to the opposite sign using the bitwise NOT operator. 
  
  def convert_using_bitwise_not(x):
      if x >= 0:
          return ~x + 1
      else:
          return ~(x-1)
  
  assert convert_using_bitwise_not(5)==-5
  assert convert_using_bitwise_not(-5)==5
  assert convert_using_bitwise_not(0)==0
  assert convert_using_bitwise_not(100)==-100
  assert convert_using_bitwise_not(-100)==100
output: def convert_using_bitwise_not(x):
      if x >= 0:
          return ~x + 1
      else:
          return ~(x-1)