#include<stdio.h>
int a[200005];
int ans[200005];
int main()
{
	int n;
	scanf("%d", &n);
	int i;
	for (i = 0; i < n; i++)
		scanf("%d", &a[i]);
	ans[n - 1] = 0;
	if (n > 1)
	{
		if (a[n - 2] > 0)
			ans[n - 2] = 1;
		else
			ans[n - 2] = 0;
	}
	for (i = n - 3; i >= 0; i--)
	{
		if (a[i] > 0 && a[i + 1] == 0)
			ans[i] = ans[i + 2] + 2;
		else if (a[i] > 0)
			ans[i] = 1;
		else
			ans[i] = 0;
	}
	long long int res = 0;
	for (i = 0; i < n; i++)
		res += ans[i];
	printf("%lld\n", res);
	return 0;
}