#include <bits/stdc++.h>
using namespace std;
ifstream fin("numarare.in");
ofstream fout("numarare.out");
int a[100001];
int n, m, k;

void Citire()
{
    fin >> n;
    for(int i = 1; i <= n;i++)  
        fin >> a[i];
}


void Rezolvare()
{
    int i, j, p, cnt = 0;
    for(p = 1;p <= n;p++)
    {
        i = p;
        j = p + 1;
        while(i > 0 && j <= n && (a[i] + a[j]) == (a[p] + a[p+1]))
            i--, j++;
        cnt += (j - i) / 2;
    }
    fout << cnt;
}

int main()
{
    Citire();
    Rezolvare();
    return 0;
}