#include <algorithm>
#include <iostream>
#include <stack>
#include <string>
#include <unordered_set>
#include <vector>

std::vector<std::string> Split(const std::string &string, const std::string &delimiter = " ") {
    std::vector<std::string> split;
    size_t prev_pos = 0;
    size_t pos = string.find(delimiter);
    while (true) {
        split.push_back(string.substr(prev_pos, pos - prev_pos));
        if (pos == std::string::npos) {
            break;
        }
        prev_pos = pos + delimiter.size();
        pos = string.find(delimiter, prev_pos);
    }
    return split;
}

std::pair<bool, int> EvaluateExpression(const std::vector<std::string> &expression) {
    std::unordered_set<std::string> operations{"+", "-", "*", "/"};
    std::vector<int> stack;
    for (auto element : expression) {
        int result;
        if (operations.count(element)) {
            if (stack.size() < 2) {
                return {false, 0};
            }
            auto first_el = stack.back();
            stack.pop_back();
            auto second_el = stack.back();
            stack.pop_back();
            if (element == "+") {
                result = first_el + second_el;
            } else if (element == "-") {
                result = -first_el + second_el;
            } else if (element == "*") {
                result = first_el * second_el;
            } else if (element == "/") {
                result = second_el / first_el - (first_el * second_el < 0);
            }
        } else {
            result = std::stoi(element);
        }
        stack.push_back(result);
    }
    if (stack.size() != 1) {
        return {false, 0};
    }
    return {true, stack.back()};
}


int main() {
    std::string expression;
    std::getline(std::cin, expression);
    auto result = EvaluateExpression(Split(expression));
    if (result.first) {
        std::cout << result.second;
    } else {
        std::cout << "ERROR";
    }
}