#include<iostream>
using namespace std;
class m{
    public:
    ststic int tp;
    static boolap(int items){
        if(items<0){
            cout<<"Invalid Production"<<endl;
            return false;
        }
        tp+=items;
        return true;
    }
};
int m::tp=0;
int main(){
    int n;
    if(!(cin>>n)) return 0;
    if(n<1||n>100) return 0;
    for(int i=0;i<n;i++){
        int items;
        if(!(cin>>items)) break;
        if(!m::ap(items)){
            return 0;
        }
    }
    cout<<m::tp<<endl;
}