// (a ≠ b ≠ c ≠ d)
        for (int a = 0; a < numbers.length; a++) {
            for (int b = 0; b < numbers.length; b++) {
                if (a != b) {
                    for (int c = 0; c < numbers.length; c++) {
                        if (a!= c && b != c) {
                            for (int d = 0; d < numbers.length; d++) {
                                if (a != d && b != d && c != d) {

                                    String left = "" + numbers[a] + numbers[b];
                                    String right = "" + numbers[c] + numbers[d];

                                    if (left.equals(right)) {
                                        foundStucks = true;
                                        System.out.printf("%d|%d==%d|%d\n", numbers[a], numbers[b], numbers[c], numbers[d]);
                                    }
                                }
                            }
                        }
                    }
                }
            }
        }