import java.io.*;
import java.util.*;

public class BinaryTreeTraversal {

    /**
     * @param args
     */
    public static void main(String[] args) {
        Scanner input = new Scanner("input.txt");
        int n = input.nextInt();
        int m = (int) Math.pow(2,n)-1;
        List<BinaryNode<Character>> list = new ArrayList<BinaryNode<Character>>();

        for (Character c : input.nextLine().toCharArray()) {
            list.add(new BinaryNode<Character>(Character.isLetter(c) ? c : null));
        }
        BinaryNode<Character> root = list.get(0);

        for (int i = 1; i <= list.size(); i++) {
            BinaryNode<Character> node = list.get(i-1);
            if (node == null)
                continue;
            node.setLeft(list.get(2*i);
            node.setRight(list.get(2*i+1);
        }

        System.out.println(root.toStringPreOrder());
        System.out.println(root.toStringInOrder());
        System.out.println(root.toStringPostOrder());
        // done!
    }
}