#include<iostream>
using namespace std;

class Factory
{
    public:
    static int totalProduction;
    
    static void addProduction(int items)
    {
        if(items < 0)
        {
            cout << "Invalid Production";
            exit(0);
        }
        totalProduction += items;
    }
};
int Factory::totalProduction = 0;

int main();
{
    int n;
    cin >> n;
    
    for(int i = 0; i < n; i++)
    {
        int items;
        cin >> n;
        Factory::addProduction(items);
    }
    cout << Factory::totalProduction;
    return 0;
}