#include <fstream>
#include <stack>
#include <queue>
#include <cmath>
#include <algorithm>
#include <iostream>
#include <set>
#include <cstring>
#include <map>
#include <string>
#include<iomanip>
#include<bitset>
#include<unordered_map>
#define oo 2000000000
#define MOD 666013
using namespace std;

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



*/
int n, a[100002],rez;
int main()
{
	int st, dr;
	fin >> n;
	for (int i = 1; i <= n; i++)
		fin >> a[i];
	for (int i = 1; i < n; i++)
	{
		int s;
		st = i;
		dr = i + 1;
		s = a[i] + a[i + 1];
		while(st > 0 && dr<=n && a[st]+a[dr]==s)
		{
			st--;
			dr++;
		}
		st++;
		dr--;
		rez += (dr - st + 1) / 2;


	}
	fout << rez;

   

}