#include <iostream>
#include <vector>
#include <algorithm>
#include <iostream>
#include <string>
#include <bitset>
#include <queue>
#include <fstream>
#include <stdio.h>
#include <string.h>
#include <iomanip>
#include <stack>
#include <climits>
#include <unordered_map>
#include <map>
#include <set>
#include <cmath>
using namespace std;

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

/*
1 2 3 4
*/

int n, a[100002];

int main()
{
	int i, st, dr, sum, ans = 0;
	fin >> n;
	for (i = 1; i <= n; i++)
		fin >> a[i];
	for (i = 1; i < n; i++)
	{
		st = i; dr = i + 1;
		sum = a[i] + a[i + 1];
		while (st > 0 && dr <= n && a[st] + a[dr] == sum)
		{
			st--; dr++;
		}
		st++; dr--;
		ans += (dr - st + 1) / 2;
	}
	fout << ans;
	return 0;
}