#include <bits/stdc++.h>

using namespace std;

ifstream f("operatii.in");
ofstream g("operatii.out");

int main()
{
    long long n, nr = 0, last = 0, x;
    f >> n;

    for(int i = 1; i <= n; i++)
    {
        f >> x;
        if(x == 0)
        {
            nr += last;
            last = 0;
        }

        last = max(last, x);
    }

    if(last != 0)
    nr += last;

    g << nr;

    return 0;
}