#include<iostream>
using namespace std;

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

int main() {
    int n, x;
    for(int i=0;i<n;i++){
    cin >> n;
    Factory::add(x);
    }
    cout << Factory::total;
}