#include<bits/stdc++.h>

 #define IOS ios::sync_with_stdio(false);//不可再使用scanf printf

 #define Max(a, b) ((a) > (b) ? (a) : (b))//禁用于函数，会超时

 #define Min(a, b) ((a) < (b) ? (a) : (b))

 #define Mem(a) memset(a, 0, sizeof(a))

 #define Dis(x, y, x1, y1) ((x - x1) * (x - x1) + (y - y1) * (y - y1))

 #define MID(l, r) ((l) + ((r) - (l)) / 2)

 #define lson ((o)<<1)

 #define rson ((o)<<1|1)

 #define Accepted 0

 #pragma comment(linker, "/STACK:102400000,102400000")//栈外挂

 using namespace std;

 inline int read()

 {

     int x=,f=;char ch=getchar();

     while (ch<''||ch>''){if (ch=='-') f=-;ch=getchar();}

     while (ch>=''&&ch<=''){x=x*+ch-'';ch=getchar();}

     return x*f;

 }

 typedef long long ll;

 const int maxn =  + ;

 const int MOD = ;//const引用更快，宏定义也更快

 const int INF = 1e9 + ;

 const double eps = 1e-;

 int a[maxn];

 int f[maxn];//f[i]表示i是否有雷

 int n;

 bool judge()

 {

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

     for(int i = ; i <= n; i++)

     {

         if(a[i] != f[i - ] + f[i] + f[i + ] || f[i] <  || f[i] > )return false;

     }

     return true;

 }

 int main()

 {

     cin >> n;

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

     int ans = ;

     f[] = ;//枚举第一行

     if(judge())ans++;

     Mem(f);

     f[] = ;

     if(judge())ans++;

     cout<<ans<<endl;

     return Accepted;

 }