#define _GLIBCXX_DEBUG
#define ll long long
#include <bits/stdc++.h>
using namespace std;
using Graph = vector<vector<int>>;

int main(){
  int N; cin >> N;
  vector<int> A;
  for(int i = 0; i < N; i++){
    string S; cin >> S;
    if(S != "+" and S != "-"){
      int s = stoi(S);
      A.push_back(s);
    }else{
      if(S == "+"){
        int a = (int)A.size();
        int X = A[a-2] + A[a-1];
        A.pop_back();
        A.pop_back();
        A.push_back(X);
      }else{
        int a = (int)A.size();
        int X = A[a-2] - A[a-1];
        A.pop_back();
        A.pop_back();
        A.push_back(X);
      }
    }
  }
  cout << A[0] << endl;
}