input: Write a python function to check whether the two numbers differ at one bit position only or not.
  assert differ_At_One_Bit_Pos(13,9) == True
  assert differ_At_One_Bit_Pos(15,8) == False
  assert differ_At_One_Bit_Pos(2,4) == False
  
output: def differ_At_One_Bit_Pos(a, b):
      xor_result = a ^ b
      return xor_result != 0 and (xor_result & (xor_result - 1)) == 0