//It is coded by Ning_Mew on 5.6
#include<bits/stdc++.h>
using namespace std;

const int maxn=1e4+7;

int n,a[maxn];
int ans=0;
int ch[maxn];

int main(){
  scanf("%d",&n);
  for(int i=1;i<=n;i++)scanf("%d",&a[i]);
  
  bool endd=true;
  memset(ch,0,sizeof(ch));
  ch[1]=1;
  for(int i=2;i<=n;i++){
    if(ch[i-1]+ch[i-2]==a[i-1])ch[i]=0;
    else{
      if(ch[i-1]+ch[i-2]==a[i-1]-1)ch[i]=1;
      else {endd=false;break;}
    }
  }
  if(endd&&ch[n-1]+ch[n]==a[n])ans++;
  
  endd=true;
  memset(ch,0,sizeof(ch));
  ch[1]=0;
  for(int i=2;i<=n;i++){
    if(ch[i-1]+ch[i-2]==a[i-1])ch[i]=0;
    else{
      if(ch[i-1]+ch[i-2]==a[i-1]-1)ch[i]=1;
      else {endd=false;break;}
    }
  }
  if(endd&&ch[n-1]+ch[n]==a[n])ans++;
  printf("%d\n",ans);
  return 0;
}