#include<stdio.h>
#define NMAX 100010

int n,v[NMAX],cent[NMAX],lung[NMAX],s[NMAX];

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

scanf("%d",&n);
for (i=1;i<=n;++i)
	scanf("%d",&v[i]);
if (n<=1000)
	{
		int s=0;
		for (i=1;i<n;++i)
			for (j=1;j<=i;++j)
					if (v[i-j+1]+v[i+j]==v[i]+v[i+1])
						++s;
				else break;
		printf("%d",s);
	}
else
	{
if (n>1) {cent[0]=1;cent[1]=1;lung[1]=1;s[1]=v[1]+v[2];}
for (i=2;i<n;++i)
{
}
	}
return 0;
}