#include <iostream>
#include <vector>
#include <string>

void solve() {
    int n;
    std::cin >> n;

    std::vector<int> stk;
    while (n--) {
        std::string s;
        std::cin >> s;

        if (s == "+") {
            int b = stk.back();
            stk.pop_back();
            int a = stk.back();
            stk.pop_back();
            stk.push_back(a + b);

        } else if (s == "-") {
            int b = stk.back();
            stk.pop_back();
            int a = stk.back();
            stk.pop_back();
            stk.push_back(a - b);

        } else {
            stk.push_back(std::stoi(s));
        }
    }

    std::cout << stk.front() << "\n";
}

int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    solve();

    return 0;
}