#include <bits/stdc++.h>

using namespace std;
ifstream fin("operatii.in");
ofstream fout("operatii.out");
int n,x,mx;
long long cnt;

int main()
{
    int i;
    fin>>n;
    for(i=1;i<=n;i++)
    {
        fin>>x;
        if(x>mx)
            mx = x;
        else if(x==0)
        {
            cnt+=mx;
            mx = 0;
        }
    }
    if(x!=0) cnt+=mx;
    fout<<cnt<<"\n";



    fout.close();
    return 0;
}