#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
int a[100010],b[100010];
int ans,n;
bool judge(int x)
{
	if(a[x-1]+a[x]+a[x+1]==b[x])
	return 1;
	else return 0;
}
void dfs(int k)
{
	if(k==n)
	{
		if(judge(n))
		ans++;
		return ;
	}
	a[k]=1;
	if(judge(k))
	dfs(k+1);
	a[k]=0;
	if(judge(k))
	dfs(k+1);
}
int main()
{
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		scanf("%d",&b[i]);
	}
	dfs(1);
	cout<<ans;
	return 0;
}