#CSP 201803-1 跳一跳

#include <stdio.h>
int main()
{
	int n=0, i, a[30], s, k = 0;
	for (i = 1; i < 30; i++)
	{
		scanf("%d", &a[i]);
		if (a[i] == 0)
		{
			n = i;
			break;
		}
	}
	if (a[0] == 1)
		s = 1;
	else if (a[0] == 2)
	{
		s = 2;
		k = 1;
	}
	else s = 0;
	for (i = 1; i <= n; i++)
		switch (a[i])
		{
		case'\0':break; break;
		case'\1': {s = s + 1, k = 0; break; }
		case'\2': {s = s + 2 + 2 * k, k++; break; }
		}
	printf("%d", s);
	return 0;
}