#include <iostream>
#include <fstream>
using namespace std;
int a[1000005];
int main()
{
    ifstream f("operatii.in");
    ofstream g("operatii.out");
    int n;
    long long s=0;
    f >> n;
    for(int i=1;i<=n;++i)
    {
        f >> a[i];
    }
    int mx=0;
    for(int i=1;i<=n;++i)
    {
        if(a[i]==0)
        {
            s=s+mx;
            mx=0;
        }
        else
        {
            if(a[i]>mx) mx=a[i];
        }

    }
    s+=mx;
    g << s;
    return 0;
}