#include <stdio.h>

long long base10to2 (int base10_number);

int main(int argc, char const *argv[]) {
  printf("%lld\n",base10to2(3));
  return 0;
}

long long base10to2 (int base10_number){
    if (base10_number == 0) {
      return 0;
    }else{
      return ( base10_number % 2 + 10 * base10to2(base10_number / 2) );
    }
}