#include <iostream>
#include <string>
#include <cstdio>
#include <stack>
#include <cstdlib>
#include <string.h>
#include <cassert>
using namespace std;

// 1 2--2+

enum Operator {
    PLUS, MINUS, MULTIPLY, DIVIDE
};

void processOperator(stack<int>& nums, Operator op) {
    if (nums.size() < 2) {
        fprintf(stderr, "Invalid RPN\n");
        exit(0);
    }

    int a = nums.top();
    nums.pop();
    int b = nums.top();
    nums.pop();
    switch (op) {
        case PLUS:
            nums.push(b + a);
            break;
        case MINUS:
            nums.push(b - a);
            break;
        case MULTIPLY:
            nums.push(b * a);
            break;
        case DIVIDE:
            nums.push(b / a);
            break;
    }
}

int main(int argc, char* argv[])
{
    if (argc != 2) {
        fprintf(stderr, "Usage: ./calc <expression>");
        exit(0);
    }

    char* exp = argv[1];
    int len = strlen(exp);

    int actNum = 0;
    stack<int> nums;
    bool minus = false;

    int i = 0;
    while (i < len) {
        if (exp[i] == '+') {
            processOperator(nums, PLUS);
            ++i;
        } else if (exp[i] == '*') {
            processOperator(nums, MULTIPLY);
            ++i;
        } else if (exp[i] == '/') {
            processOperator(nums, DIVIDE);
            ++i;
        } else if (exp[i] == '-') {
            if (i < len && isdigit(exp[i + 1])) {
                minus = true;
                ++i;
            } else {
                processOperator(nums, MINUS);
                ++i;
            }
        } else if (isdigit(exp[i])) {
            while (isdigit(exp[i]) && i < len) {
                actNum *= 10;
                actNum += (exp[i] - '0');
                ++i;
            }

            if (minus)
                actNum *= -1;

            nums.push(actNum);

            minus = false;
            actNum = 0;
        } else
            ++i;
    }

    if (nums.size() != 1) {
        fprintf(stderr, "Invalid RPN\n");
        exit(0);
    }

    cout << nums.top() <<endl;

    return 0;
}