reverse binary

#include <stdio.h>
#include <stdlib.h>

int reversebinary(int n){
   int i, bit, skip=1;
   int bits=31, bits_to_skip=bits;
   int result=0;

   for(i=bits; i>=0; i--){
      bit = n & (1 << i);
      if(bit && skip == 1){
         skip = 0;
         bits_to_skip = i;
      }

      if(skip == 0 && bit) result |= 1 << (bits_to_skip-i);
   }

   return result;
}

int main(int argc, char **argv){
   int n=0;

   if (argc < 2){
      printf("usage: %s <number>\n", argv[0]);
      return -1;
   }

   n = atoi(argv[1]);

   if(n < 1 || n > 1000000000){
      printf("invalid number: %s, it must be 1 ≤ n ≤ 1000000000\n", argv[1]);
      return -1;
   }

   printf("%d\n", reversebinary(n));

   return 0;
}