#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,items;
    cin>>n;
    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;
}