#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("YES");}else{puts("NO");}
#define MAX_N 200005

int main() {
    int n;
    cin >> n;
    string s[n];
    rep(i,n) cin >> s[i];
    int a[10000] = {};
    int now = 0;
    rep(i,n){
        if(s[i] == "+"){
            a[now-2] = a[now-2] + a[now-1];
            now--;
        }else if(s[i] == "-"){
            a[now-2] = a[now-2] - a[now-1];
            now--;
        }else{
            int x = 0;
            rep(j,s[i].size()){
                x *= 10;
                x += s[i][j] - '0';
            }
            a[now] = x;
            now++;
        }
    }
    cout << a[0] << endl;
    return 0;
}