Consider the following C++ function $f()$:

unsigned int f(unsigned int n) {
unsigned int b = 0;
while (n) {
b = b + (n bitwise AND 1);
n = n shifted right by 1;
}
return b;
}

The function $f()$ returns the integer that represents the $P$ in the binary representation of positive integer $n$, where $P$ is: