#include <iostream>
#include <vector>
#include <string>
#include <utility>
#include <algorithm>
#include <climits>
#include <map>
#include <queue>
#include <cmath>
#include <set>
#include <stdexcept>

using namespace std;

using int64 = long long;


int main() {
    int n;
    cin >> n;
    vector<int> st;
    for (int i=0; i<n; i++) {
        string c;
        cin >> c;
        if (c == "+" || c == "-") {
            int b = st.back(); st.pop_back();
            int a = st.back(); st.pop_back();
            int t = (c=="+"? a+b : a-b);
            st.push_back(t);
        } else {
            st.push_back(stoi(c));
        }
    }

    cout << st.back() << endl;
}