import java.util.*;

class Langford {
    private static char[] empty(int length) {
        char[] chars = new char[length];
        Arrays.fill(chars, '#');
        return chars;
    }

    private static int alphabetPosition(char c) {
        c = Character.toUpperCase(c);
        return c - 64;
    }

    private static char letterValue(int n) {
        return (char) (n + 64);
    }

    private static List<char[]> blank(int order, char letter) {
        char[] blank = empty(2 * order);
        return potentialPosition(blank, letter);
    }

    private static List<char[]> potentialPosition(char[] langford, char letter) {

        final int LENGTH = langford.length;

        List<char[]> langfords = new ArrayList<>();
        int v = alphabetPosition(letter);

        for (int i = 0; i < LENGTH - v - 1; i++) {
            int left = i;
            int right = i + v + 1;
            if (!Character.isLetter(langford[left]) && !Character.isLetter(langford[right])) {
                char[] temp = langford.clone();
                temp[left] = letter;
                temp[right] = letter;
                langfords.add(temp);
            }
        }
        return langfords;
    }

    public static void langfordStrings(int order) {
        boolean isValidOrder = (order % 4 == 0 || order % 4 == 3);
        if (!isValidOrder) {
            throw new IllegalArgumentException("Order must be a multiple of 4 or one less than a multiple of 4");
        }

        List<char[]> squareOne = blank(order, 'A');
        List<char[]> temp = new ArrayList<>();
        for (char c = letterValue(order); c >= 'B'; c--) {
            for (char[] C : squareOne) {
                temp.addAll(potentialPosition(C, c));
            }
            squareOne.clear();
            squareOne.addAll(temp);
            temp.clear();
        }
        for (char[] C : squareOne) {
            System.out.println(String.valueOf(C));
        }
    }
}

class Main {
    public static void main(String args[]) {
        Langford.langfordStrings(8);
    }
}