#include <iostream>

 #include <cstdio>

 #include <cstring>

 using namespace std;

 int a[],n,m,f[],ans;

 bool cal()

 {

     for (int i=;i<=n;i++)    {f[i+]=a[i]-f[i]-f[i-];}

     if (a[n]-f[n]-f[n-]) return ;

     else return ;

 }

 int main()

 {

     scanf("%d",&n);

     for (int i=;i<=n;i++)    scanf("%d",&a[i]);

     if (a[]==) ans+=cal();

     else if (a[]==)

     {

         f[]=;

         ans+=cal();

         memset(f,,sizeof(f));

         f[]=;

         ans+=cal();

     }

     else

     {

         f[]=f[]=;

         ans+=cal();

     }

     printf("%d\n",ans);

     return ;

 }