public class Arithmetique {
    public static void main(String[] args) {
        ChainePile<Integer> pile = new ChainePile<>();

        for (String arg : args) {
            try {
                int n = Integer.parseInt(arg);
                pile.addFirst(n);
            } catch (NumberFormatException e) {
                if (pile.size() < 2) {
                    System.err.println("Invalid stack size.");
                    return;
                }
                
                int n2 = pile.pollFirst();
                int n1 = pile.pollFirst();

                switch (arg) {
                    case "+":
                        pile.addFirst(n1 + n2);
                        break;

                    case "-":
                        pile.addFirst(n1 - n2);
                        break;

                    case "/":
                        pile.addFirst(n1 / n2);
                        break;

                    case "x":
                        pile.addFirst(n1 * n2);
                        break;

                    default:
                        System.err.println("Invalid operator");
                        return;
                }
            }
        }

        System.out.println(pile.pollFirst());
    }
}