#include<iostream>
using namespace std;
class factory
{
    private:
    static int total;
    public:
    static void add(int items)
    {
      total+=items;
    }
    static int gt()
    {
        return total;
    }
};
int main()
{
int n;
cin>>n;
int items;
for(int i=0;i<n;i++)
{
    cin>>items;
    if(items<0)
    {
        cout<<"Invalid Production"<<endl;
        return 0;
    }
    factory::add(items);
}
cout<<factory::gt();
return 0;
}