private boolean isPossibleBlock(int[][] game, int x, int y, int number) {
        int x1 = x < 3 ? 0 : x < 6 ? 3 : 6;
        int y1 = y < 3 ? 0 : y < 6 ? 3 : 6;
        for (int yy = y1; yy < y1 + 3; yy++) {
            for (int xx = x1; xx < x1 + 3; xx++) {
                if (game[yy][xx] == number)
                    return false;
            }
        }
        return true;
    }