#include<iostream>
using namespace std;
class factory{
    private:
    static int total'
    
    public:
    static void add(int items){
        total+=items;
    }
    static int gettotal(){
        return total;
    }
};

int factory::total=0;
int main(){
    if(!(cin>>n)||n<1||n>100)
      return 0;
    for(int i=0;i<n;i++){
        int items;
        
        if(!(cin>>items))
         return 0;
        
        if(items<0){
            cout<<"Invalid Production";
            return 0;
        }
        factory::add(items);
    }
    cout<<factory::gettotal();
    
    return 0;
}