min amount

class Result {

    /*
     * Complete the 'calculateAmount' function below.
     *
     * The function is expected to return a LONG_INTEGER.
     * The function accepts INTEGER_ARRAY prices as parameter.
     */

    public static long calculateAmount(List<Integer> prices) {
    // Write your code here
        List<Integer> discount = new ArrayList();
        long cost = 0L;
        for (int i = 0 ; i < prices.size(); i++) {
            Integer price = prices.get(i);
            if (i == 0) {
                discount.add(price);
                cost = cost + price;
                continue;
            } 
            Integer min = Collections.min(discount);
        
            if (prices.get(i) > min) {
                cost = cost + (prices.get(i) - min);
                discount.add(price);
            } 
            if (prices.get(i) < min) {
                cost = cost + 0;
                discount.add(price);
            }
        }
        return cost;
    }

}