#include<iostream>
using namespace std;
void addProduction(int x)
{
    static int sum=0;
    if(x<0)
    {
        cout<<"Invalid Production";
        exit(0);
    }
    sum+=x;
    //cout.flush();
    //if(cin.peek()==EOF)
    //cout<<total;
    return sum;
}
int main()
{
int n,x,ans=0;
cin>>n;
for(int i=0;i<n;i++)
{
    cin>>x;
    ans=addProduction(x);
    //addProduction(x);
}
cout<<ans;
return 0;
}