/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	static int move=0;
	public static void main (String[] args) throws java.lang.Exception
	{
		System.out.println(solve(2,"A","B","C"));
		move = 0;
		System.out.println(solve(3,"A","B","C"));
		move = 0;
		System.out.println(solve(4,"A","B","C"));
	}
 
	public static String solve(int n, String start, String middle, String end) {
     if (n == 1) {
        move++;
        return Integer.toString(move);
     }
 
     solve(n - 1, start, end, middle);
     move++;
     return solve(n - 1, middle, start, end);
} 
}

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