Count Set Bits in an Integer

#include <stdio.h>

int countSetBits(unsigned int n) {
    // Write your code here
    int len_n = sizeof(n) * 8;
    int output = 0;
    while(len_n > 0){
        if(n & 1 == 1){
            output++;
        }
        n >>= 1;
        len_n--;
    }
    return output;
}

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