#include <bits/stdc++.h>
using namespace std;

int main()
{
    stack<int> num;
    
    int n;
    cin >> n;
    for (int i = 1; i <= n; i++)
    {
        string key;
        cin >> key;
        
        if (key == "+")
        {
            int temp1, temp2;
            temp2 = num.top();
            num.pop();
            temp1 = num.top();
            num.push(temp2);
            num.push(temp1 + temp2);
        }
        else if (key == "D")
        {
            num.push(num.top() * 2);
        }
        else if (key == "C")
        {
            num.pop();
        }
        else
        {
        	num.push(stoi(key));
		}
    }
    
    int sum = 0;
    while (!num.empty())
    {
        sum += num.top();
        num.pop();
    }
    cout << sum;
}