#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>
#include <cmath>
#include <bitset>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <algorithm>
#include <complex>
#include <unordered_map>
#include <unordered_set>
#include <random>
#include <cassert>
#include <fstream>
#include <utility>
#include <functional>
#include <time.h>
#include <stack>
#include <array>
#define popcount __builtin_popcount
using namespace std;
typedef long long int ll;
typedef pair<int, int> P;

int main()
{
	int n; cin>>n;
	vector<ll> v;
	for(int i=0; i<n; i++){
		string a; cin>>a;
		if(a=="+"){
			int y=v.back(); v.pop_back();
			int x=v.back(); v.pop_back();
			v.push_back(x+y);
		}else if(a=="-"){
			int y=v.back(); v.pop_back();
			int x=v.back(); v.pop_back();
			v.push_back(x-y);
		}else{
			int x=0;
			for(int j=0; j<a.size(); j++){
				x*=10;
				x+=(int)(a[j]-'0');
			}
			v.push_back(x);
		}
	}
	cout<<v[0]<<endl;
	return 0;
}