Write a function to determine the number of bits you would need to flip to convert integer A to integer B.

Example1:

 Input: A = 29 (0b11101), B = 15 (0b01111)

 Output: 2

Example2:

 Input: A = 1，B = 2

 Output: 2

Note:

1. -2147483648 <= A, B <= 2147483647