public class tiles {

    public static void main (String[] args) {

	/* convert _87654321 into 3x3 grid
	 *   
	 * 1 2 3
	 * 4 5 6
	 * 7 8 _
	 *
	 */

	// let 9 be the "empty" spot

	/* algorithm:
	   - build an empty string
           - copy and store the original number
	   - if we still have a number left (if copy is not zero)
	     - divide the number by 10
	     - take the remainder and append to the string
	     - subtract the remainder from the copy
             - divide the number by 10 and make that the number
           - repeat
	   
	   To take the reminder,
	    - num % 10 gives the current remainder (1 digit)
	*/
	
	final int ORIG  = 987654321; // preserve original number
	int copy = ORIG;             // use copy to "destroy" to make the number
	int rem;                     // remainder so far (none)
	String s = "";               // String version of the number
	int size = (int) Math.sqrt((""+ORIG).length()); // size of square grid
	int count = 0;               // current # of elements processed in row

	// build grid:
	while (copy!=0) {

	    // retrieve current digit:
	    rem = copy % 10; 
	    copy -= rem;    
	    copy = copy/10;  // note: integer division!

	    // adjust for blank
	    if (rem==9) s += " ";
	    else s += rem;

	    // adjust for new line (end of row)
	    count++;
	    if (count==size) { s +="\n"; count = 0; }

	}

	System.out.println(s);

	// Note: Using a for-loop would certainly help.
	// Why didn't I? I avoid the problem of an out-of-bounds int.
	// Realistically, you would use a for-loop though :-)

    }

}