public static int pickingNumbers(List<Integer> a) {
    // Write your code here
        int max = Integer.MIN_VALUE; 
        Map<Integer,List<Integer>> maps = new HashMap<>();
        for (Integer e : a) {
            if (maps.containsKey(e)) {
                List<Integer> list = maps.get(e);
                list.add(e);
                maps.put(e, list);
            }
            else{
                List<Integer> list = new ArrayList<>();
                list.addAll(a.stream().filter(element->element==e+1).collect(Collectors.toList()));
                maps.put(e, list);
            }
        }
        for (Map.Entry<Integer,List<Integer>> entry : maps.entrySet()) {
            if(entry.getValue().size()+1 > max){
                max = entry.getValue().size()+1;
            }
        }
        return max;
    }