Count Set Bits in an Integer

#include <stdio.h>

int countSetBits(unsigned int n) {
    unsigned int w = 0;
    for(int a = 0; a < 32; a++)
    {
        if((n >> a) & 1)
        w++;
    }
    return w;
}

int main() {
    int n;
    scanf("%d", &n);
    printf("%d", countSetBits(n));
    return 0;
}