#include <bits/stdc++.h>
using namespace std;
ifstream fin("numarare.in");
ofstream fout("numarare.out");
int a[100005], n;

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] = 300000;
	for(i = 2; i <= n; i++)
	{
		st = i - 1; dr = i;
		while (a[st] + a[dr] == a[i] + a[i - 1])
		{
			st--;
			dr++;
		}
		st++; dr--;
		S += (dr - st + 1) / 2;
	}
	fout << S << "\n";
	return 0;
}