#include <iostream>
#include <fstream>
using namespace std;

ifstream fin("numarare.in");
ofstream fout("numarare.out");

int a[100005], n;

int main()
{
	int i, j, cnt = 0;
	fin >> n;
	for (i = 1; i <= n; i++)
		fin >> a[i];
	for (i = 1; i <= n; i++)
		for (j = 0; i + j + 1 <= n && i - j > 0 &&
			(a[i-j] + a[i + j + 1] == a[i] + a[i+1]); j++)
			cnt++;
	fout << cnt;
}