public static long stockmax(List<Integer> prices) {
        long maxProfit = 0;
        int maxFuturePrice = 0;

        for (int i = prices.size() - 1; i >= 0; i--) {
            if (prices.get(i) > maxFuturePrice) {
                maxFuturePrice = prices.get(i);
            }
            maxProfit += maxFuturePrice - prices.get(i);
        }

        return maxProfit;
    }