#include<iostream>
using namespace std;
class Machine {
private:
    int itempro;
    static int totalpro;
public:
    void recordpro(int items){
        if (items < 0) {
            cout<<"Invalid Production"<< endl;
        }else {
            itempro = items;
            totalpro += items;
        }
        }
    static int getTotalpto(){
        return totalpro;
    }
};
int Machine::totalProduction = 0;
int main()
{
    int n;
    cin>>n;
    Machine m;
    for (int i=0;i<n;i++){
        int iteams;
        cin>>items:
        m.recordpro(iteams);
    }
    cout<< Machine::getTotalpro() << endl;
    return 0;
    
}