public static void main(String[] args) {

        int maxCount = Integer.valueOf(args[0]);

        List<Integer> list = new ArrayList<Integer>(maxCount);
        StringBuilder naturalOrder = new StringBuilder(maxCount + maxCount - 1);
        StringBuilder reverseOrder = new StringBuilder(maxCount + maxCount - 1);

        for(int i=1; i<=maxCount; i++){
            list.add(i);
            if(i > 1){
                naturalOrder.append("-");
                reverseOrder.insert(0, "-");
            }
            naturalOrder.append(i);
            reverseOrder.insert(0, i);

            if(i%2 == 0){
                System.out.println(reverseOrder);
            } else {
                System.out.println(naturalOrder);
            }
        }
    }