"""
Write a function that takes an unsigned integer and returns the number of 1 bits it has.

Example:

The 32-bit integer 11 has binary representation

00000000000000000000000000001011
so the function should return 3.
"""
class Solution:
    # @param A : integer
    # @return an integer
    def numSetBits(self, A):
        count=0
        for i in range(31,-1,-1):
            if A &(1<<i)!=0:
                count+=1
        return count
