#include <iostream>
#include <fstream>

using namespace std;

int main() {
long int n, i, s, x, maxim;
s = 0;
ifstream in ("operatii.in");
ofstream out ("operatii.out");
in >> n;
maxim = 0;
for (i = 0; i < n; i++)
{
	in >> x;
	if (x == 0)
	{
		s += maxim;
		maxim = 0;
	}
	else
	{
		if (maxim  < x)
			maxim  = x;
	}
}
s += maxim;
out << s;
return 0;
}