import java.util.Scanner;
import java.util.Stack;

public class PostFixEvaluator {

    public static double evaluate(String expression) {
        Scanner scanner = new Scanner(expression);
        Stack<Double> operands = new Stack<Double>();
        
        while (scanner.hasNext()) {
            if (scanner.hasNextDouble()) {  // i.e., operand was seen
                operands.push(scanner.nextDouble());
            }
            else {  // i.e., an operator was seen
                String operator = scanner.next();
                double operand1 = operands.pop();
                double operand0 = operands.pop();
                
                switch (operator) {
                case "+" : operands.push(operand0 + operand1); break;
                case "-" : operands.push(operand0 - operand1); break;
                case "*" : operands.push(operand0 * operand1); break;
                case "/" : operands.push(operand0 / operand1); break;
                case "^" : operands.push(Math.pow(operand0,operand1));
                }
            }
        }
        scanner.close();
        return operands.pop();
    }
    
    public static void main(String[] args) {
       System.out.println("Enter a postfix expression:");    
       Scanner scanner = new Scanner(System.in);
       String inputStr = scanner.nextLine();
       scanner.close();
       System.out.println(PostFixEvaluator.evaluate(inputStr));
    }

}