#include<algorithm>
using namespace std;
#define N_MAX 100005
int a[N_MAX],n,i,j,k,s;
long long rez;

float modul(float x)
{
	if(x<0)
		return -x;
	return x;
}

int main()
{
	freopen("numarare.in","r",stdin);
	freopen("numarare.out","w",stdout);

	scanf("%d",&n);
	for(i=1;i<=n;i++)
	{
		scanf("%d",&a[i]);
	}

	for(k=1;k<n;k++)
	{
		i=k;	j=k+1;	s=a[i]+a[j];	rez++;
		while(i>1&&j<n&&s==a[i-1]+a[j+1])
			i--,j++,rez++;
	}

	/*printf("100000\n");
	for(i=1;i<=100000;i++)
		printf("%d ",i);
		*/
	printf("%lld\n",rez);
	return 0;
}