Write a function that takes the binary representation of a positive integer and returns the number of set bits it has (also known as the Hamming weight).

Examples

Example 1

Input:  n = 11
Output: 3

The input binary string 1011 has a total of three set bits.

Example 2

Input:  n = 128
Output: 1

The input binary string 10000000 has a total of one set bit.

Example 3

Input:  n = 2147483645
Output: 30

The input binary string 1111111111111111111111111111101 has a total of thirty set bits.

Constraints

• 1 <= n <= 2³¹ - 1

Follow up

If this function is called many times, how would you optimize it?