#include<iostream>
using namespace std;
int main()
{
    int a;
    cin>>a;
    int b[a],sum=0;
    if(a<0)
    {
        cout<<"Invalid input";
        return 0;
    }
    for(i=0;i<a;i++)
    {
        cin>>b[i];
        if(b[i]<0)
        {
            cout<<"Invalid input";
            return 0;
        }
        sum+=b[i];
        
    }
    cout<<sum;
}