import java.util.Iterator;
import java.util.LinkedList;
import java.util.Queue;
import java.util.Stack;

public class QueueUtils {

    private static int n1, n2;

    public static Queue<String> build(String line) {
        Queue<String> data = new LinkedList<>();
        String[] tokens = line.split("\\s+");

        for (String temp : tokens) {
            data.add(temp);
        }
        return data;
    }

    public static int eval(Queue<String> line) throws Exception {
        int calc = 0;
        Stack<String> numbers = new Stack<>();
        Stack<String> operators = new Stack<>();

        for (String node : line) {
            String isNumber = ".*[0-9].*";

            if (node.matches(isNumber))
                numbers.push(node);
            else
                operators.push(node);
        }

        n2 = Integer.parseInt(numbers.peek()); numbers.pop();
        if (!numbers.isEmpty()) {
            n1 = Integer.parseInt(numbers.peek()); numbers.pop();
        }

        for (String oprts : operators) {
            switch(oprts) {
                case "+":
                    calc = (n1 + n2);
                    break;
                case "-":
                    calc = (n1 - n2);
                    break;
                case "*":
                    calc = (n1 * n2);
                    break;
                case "/":
                    calc = (n1 / n2);
                    break;
            }
        }

        return operators.size() > 0 ? calc : n2;
    }

}