public boolean isNatural(){
        switch (value){
            case 2:
                return true;
            case 0:
                return true;
            case -2:
                return true;
            case -4:
                return true;
            case -5:
                return true;
            case -7:
                return true;
            case -9:
                return true;
            default:
                return false;
        }
    }