#include <bits/stdc++.h>
#define PI 3.14159265359
#define NIL -1
using namespace std;
const int64_t MOD = 1e9 + 7;

int main() {
	int N;
	cin >> N;

	vector<string> v;
	for (int i = 0; i < N; i++) {
		string S;
		cin >> S;
		//cout << S << endl;

		if ((S == "+")|| (S == "-")) {
			int a, b, c;
			a = stoi(v.at(v.size() - 2));
			b = stoi(v.at(v.size() - 1));

			if (S == "+") c = a + b;
			else c = a - b;

			string ans = to_string(c);
			v.pop_back();
			v.at(v.size() - 1) = ans;
		}
		else {
			v.push_back(S);
		}
	}

	cout << v.at(0) << endl;
}