// Author          : Apostolos Syropoulos
// Program         : Iterative solution of the towers of hanoi problem
//                   using bitwise operators.
// Date            : November 26, 2000
//
import java.io.*;

public class hanoiG1
{
  static int moves=0; //number of moves so far
       static int getInt()
       {
           String line;
           BufferedReader in = 
           new BufferedReader(new InputStreamReader(System.in)); 
           try
           {
              line = in.readLine();
              int i = Integer.valueOf(line).intValue();
              return i;
           }
           catch (Exception e)
           {
              System.err.println("***Error: Input is not a number.\n" +
                                 "Input assumed to be the number 1");
              return 1;
           }
       }

       static void hanoi(int height)
       {
 
            for (int x=1; x < (1 << height); x++) 
                moveDisk((char)((x&x-1)%3+65),(char)((((x|x-1)+1)%3)+65));
       }

       static void moveDisk(char fromPole, char toPole)
       {
            moves++;
            System.out.print(fromPole);
            System.out.print(toPole);
            System.out.print(((moves % 20)==0) ? '\n' : ' ');
       }

       public static void main(String[] args)
       {
            long time1, time2; //for benchmarking
            int TowerHeight;

            System.out.println("Enter Tower height...");
            System.out.print("?");
            TowerHeight = getInt();
            time1 = System.currentTimeMillis();
            hanoi(TowerHeight);
            time2 = System.currentTimeMillis();
            System.out.println();
            System.out.print(time2-time1); //print execution time in msec
            System.out.println(" msec execution time");
       }

}