#include <bits/stdc++.h>
using namespace std;

/// O(n^2)

const int MAX = 100005;
int a[MAX];

int main()
{
    ifstream cin("numarare.in");
    ofstream cout("numarare.out");
    int n;
    cin >> n;

    for (int i = 1; i <= n; ++i)
        cin >> a[i];

    int ans = 0;
    for (int i = 1; i <= n; ++i)
    {
        int left = i, right = i+1;
        while (left >= 1 && right <= n && a[left]+a[right] == a[i]+a[i+1])
        {
            --left;
            ++right;
        }
        ans += (right - left - 1) / 2;
    }

    cout << ans;

    return 0;
}