public static int activityNotifications(List<Integer> expenditure, int d) {
        var list = new ArrayList<Integer>();
        int notifications = 0;

        Function<List<Integer>, Double> medFunc;
        if (d % 2 == 0) {
            medFunc = (arr) -> ((arr.get(d / 2) + arr.get(d / 2 - 1)) / 2.);
        } else {
            medFunc = (arr) -> (double) arr.get(d / 2);
        }

        var indexToRemove = 0;
        for (var i = 0; i < expenditure.size(); i++) {
            if (i < d) {
                add(expenditure.get(i), list);
            } else {
                double med = medFunc.apply(list);
                if (med * 2 <= expenditure.get(i)) {
                    notifications++;
                }

                if (i < expenditure.size() - 1) {
                    add(expenditure.get(i), list);
                    remove(expenditure.get(indexToRemove), list);
                    indexToRemove++;
                }
            }
        }

        return notifications;
    }

    public static void add(Integer value, List<Integer> list) {
        int index = Collections.binarySearch(list, value);

        // If value is not found, binarySearch returns (-(insertion point) - 1)
        if (index < 0) {
            index = -(index + 1);
        }

        list.add(index, value);
    }

    public static void remove(Integer value, List<Integer> list) {
        int index = Collections.binarySearch(list, value);
        if (index >= 0) {
            list.remove(index);
        }
    }