#include <bits/stdc++.h>
using namespace std;
ifstream in("operatii.in");
ofstream out("operatii.out");
int main()
{
    int n;
    in >> n;
    int mx = 0, s = 0;
    for(int i = 1; i <= n; i ++)
    {
        int a;
        in >> a;
        if(a == 0)
        {
            s += mx;
            mx = 0;
        }
        mx = max(mx, a);
    }
    s += mx;
    out << s;
    return 0;
}