#include<iostream>                          
using namespace std;
class Factory{
private:
     static int totalProduction;
public:
     static void addProduction (int items){
         if (items<0){
             cout<,"Invalid Production";
             exit(0);
         }
         totalProduction +=items;
     }
     static int getTotalProduction(){
         return totalProduction;
     }
};
int Factory::totalProduction =0;
int main(){
    int n;
    cin>>n;
    for (int i=0;i<n;i++){
        int items;
        cin>>items;
        Factory :: addProduction(items);
    }
    cout<<Factory::getTotalProduction();
    return 0;
}