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

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

int n, a[100005];

int main()
{
	int i, st, dr;
	long long s = 0;
	fin >> n;
	for (i = 1; i <= n; i++)
		fin >> a[i];

	a[0] = a[n + 1] = 2e9;
	for (i = 1; i < n; i++)
	{
		st = i; dr = i + 1;
		while (a[st] + a[dr] == a[i] + a[i + 1])
		{
			st--;
			dr++;
		}
		s += (dr - st) / 2;
	}
	fout << s << "\n";
	return 0;
}