#include <fstream>
using namespace std;
ifstream fin("operatii.in");
ofstream fout("operatii.out");

void motorization(int n) {
    unsigned int mx = 0, sum = 0;
    for (int i = 1; i <= n; ++i) {
        int x;
        fin >> x;
        if (x == 0) {
            sum += mx;
            mx = 0;
            continue;
        }
        (mx < x)? mx = x: true;
        if (i == n)
            sum += mx;
    }
    fout << sum;
}

int main()
{
    int n;
    fin >> n;
    motorization(n);
    return 0;
}