least sig nib

#include <stdio.h>

void printBits(unsigned x) {
  for (int i = sizeof(x) * 8 - 1; i >= 0; i--) {
    printf("%d", 1 & (x >> i));
    if (i % 4 == 0) {
      putchar(' ');
    }
  }
  puts("");
}

int lsNib(unsigned a) {
  const unsigned mask = (1 << 4) - 1;
  const int nibNr = sizeof(a) * 2;
  int pos = nibNr;
  for (int i = 0; i < nibNr; i++) {
    if ((a >> (i * 4)) & mask) {
      pos = i;
      break;
    }
  }
  return pos;
}

int main(void) {
  unsigned a;
  scanf("%u", &a);
  printBits(a);
  printf("%d\n", lsNib(a));
  return 0;
}