public static List<Double> runningMedian(List<Integer> a) {
            List<Double> medians = new ArrayList<>();
            PriorityQueue<Integer> lower = new PriorityQueue<>(Collections.reverseOrder());
            PriorityQueue<Integer> upper = new PriorityQueue<>();

            for (int num : a) {
                if (lower.isEmpty() || num <= lower.peek()) {
                    lower.offer(num);
                } else {
                    upper.offer(num);
                }

                if (lower.size() > upper.size() + 1) {
                    upper.offer(lower.poll());
                } else if (upper.size() > lower.size()) {
                    lower.offer(upper.poll());
                }

                if (lower.size() == upper.size()) {
                    medians.add((lower.peek() + upper.peek()) / 2.0);
                } else {
                    medians.add((double) lower.peek());
                }
            }
            return medians;
        }