#include<iostream>
using namespace std;
class Machine
{
    private:
    int itemp;
    static int tprod;
    public:
    void rprod(int items)
    {
        if(items<0)
        {
            cout<<"Invalid Production"<<endl;
        }
        else
        {
            itemp=items;
            tprod+=items;
        }
    }
    static int gtprod()
    {
        return tprod;
    }
};
int Machine::tprod=0;
int main()
{
    int n;
    cin>>n;
    Machine m;
    for(int i=0;i<n;i++)
    {
        int items;
        cin>>items;
        m.rprod(items);
    }
    cout<Machine::gtprod()<<endl;
    return 0;
}