#include <stdio.h>

void
itob(int n)
{
	for (int i = 15; i >= 0; --i) {
		int j = n >> i;
		if (j & 1) {
			printf("1");
		} else {
			printf("0");
		}
	}
	printf("\n");
}

/*
 * return x with the n bits that begin at position p inverted, leaving the other
 * bits unchanged
 */
void
invert(unsigned x, int p, int n)
{
	int i;
	i = 0;
	while (n > 0) {
		i |= 1 << p;
		--p;
		--n;
	}
	x ^= i;
}

/*
 * return x with the n bits that begin at position p set to the rightmost n bits
 * of y, leaving the other bits unchanged
 */
void
setbits(unsigned x, int p, int n, unsigned y)
{
	x = x >> (p + 1 - n) & ~(~0 << n);
	y = y & (~0 << n) | x;
	printf("%d %d\n", x, y);
	itob(x);
	itob(y);
}

/* count the number of 1-bits */
int
bitcount(unsigned x)
{
	int b = 0;
	while (x != 0) {
		/* deletes rightmost 1-bit in x */
		x &= (x - 1);
		++b;
	}
	return b;
}

int
main()
{
	/* setbits(5, 2, 3, 16); */
	/* invert(16, 2, 1); */
	printf("%d\n", bitcount(4));
	return 0;
}