Write a program to swap odd and even bits in an integer with as few instructions as possible (e.g., bit 0 and bit 1 are swapped, bit 2 and bit 3 are swapped, and so on).

Example1:

 Input: num = 2（0b10）

 Output 1 (0b01)

Example2:

 Input: num = 3

 Output: 3

Note:

1. 0 <= num <= 2^30 - 1
2. The result integer fits into 32-bit integer.