#include<iostream>
using namespace std;
int main(){
    int n;
    cin >> n;
    if(n<0) {
        cout <<"Invalid input";
        return 0;
    }
    int amnt, sum = 0;
    for(int i = 0;  i< 0; i ++){
        cin >> amnt;
        if(amnt < 0){
            cout << "Inavalid input";
            retutn 0;
        }
        sum += amnt;
    }
    cout << sum ;
    return 0;
}