private String getLetter18(int x) {
        switch (x) {
            case 1:
                return "a";
            case 2:
                return "b";
            case 3:
                return "c";
            case 4:
                return "d";
            case 5:
                return "e";
            case 6:
                return "f";
            case 7:
                return "g";
            case 8:
                return "h";
        }
        return null;

    }