#include <iostream.h>
#include <stdlib.h>

void print_binary_digit(int x)
{
  switch(x) {
  case 0: cout << "0"; break;
  case 1: cout << "1"; break;
  default:
    cout << "Error, print_digit accepts 0-15 only\n";
    exit(-1);
    break;
  }
}