public class Exercise12 {

  public static int mystery(int n) {
    return search(1, n, n);
  }  // end mystery

  private static int search(int first, int last, int n) {
    int returnValue;
    System.out.println("Enter: first = " + first + 
                       " last = " + last);
    int mid = (first + last)/2;
    if ((mid * mid <= n) && (n < (mid+1) * (mid+1))) {
      returnValue = mid;
    }
    else if (mid * mid > n) {
      returnValue = search(first, mid-1, n);
    }
    else {
      returnValue = search(mid+1, last, n);
    }  // end if
    System.out.println("Leave: first = " + first +
                       " last = " + last);
    return returnValue;
  }  // end search

  public static void main(String[] args) {
    System.out.println(mystery(30));
  }  // end main
}  //end Exercise12