import java.util.Stack;

class Demo {
    static int postfixEval(String s) {
	Stack stk = new Stack();
	for (int i = 0; i < s.length(); i++) {
	    char sym  = s.charAt(i);
	    if (Character.isDigit(sym))
		stk.push(new Integer(Character.digit(sym,10)));
	    else {
		int rightVal = ((Integer)(stk.pop())).intValue();
		int leftVal = ((Integer)(stk.pop())).intValue();
		int result = 0;
		if (sym == '+')
		    result = leftVal + rightVal;
		else if (sym == '-')
		    result = leftVal - rightVal;
		else if (sym == '*')
		    result = leftVal * rightVal;
		else if (sym == '/')
		    result = leftVal / rightVal;
		stk.push(new Integer(result));
	    }
	}
	return ((Integer)(stk.pop())).intValue();
    }

    static int precedence(char c) {
	switch (c) {
	case '+': case '-': return 5;
	case '*': case '/': return 10;
	default: throw new IllegalArgumentException();
	}
    }

    static String infixToPostfix(String infix) {
	Stack stk = new Stack();
	String postfix = "";
	for (int i = 0; i < infix.length(); i++) {
	    char sym  = infix.charAt(i);
	    if (Character.isDigit(sym))
		postfix += sym;
	    else {
		while (!stk.empty()) {
		    char top = ((Character)(stk.peek())).charValue();
		    if (precedence(top) < precedence(sym))
			break;
		    postfix += top;
		    stk.pop();
		}
		stk.push(new Character(sym));
	    }
	}
	while (!stk.empty()) {
	    char top = ((Character)(stk.pop())).charValue();
	    postfix += top;
	}
	return postfix;
    }

    public static void main (String[] args) {

	System.out.println("postfix: " + args[0]);
	System.out.println("value: " + postfixEval(args[0]));
	/*
	*/

	/*
	System.out.println("infix: " + args[0]);
	System.out.println("postfix: " + infixToPostfix(args[0]));
	System.out.println("value: " + postfixEval(infixToPostfix(args[0])));
	*/

	/*
	System.out.println("24+ = " + postfixEval("24+"));
	System.out.println("24+8* = " + postfixEval("24+8*"));
	System.out.println("24+8*2/ = " + postfixEval("24+8*2/"));
	
	System.out.println("1+2*3 = " + infixToPostfix("1+2*3"));
	System.out.println("1*2+3 = " + infixToPostfix("1*2+3"));
	System.out.println("1+2+3 = " + infixToPostfix("1+2+3"));
	*/
    }
}