#include <bits/stdc++.h>
#define MOD 20173333
using namespace std;

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

int n;
int s[100005];

int main()
{
    int i, x, y, cnt;
    fin >> n;
    for (i = 1; i <= n; i++)
        fin >> s[i];

    cnt = 0;
    for (i = 1; i <= n; i++)
    {
        x = i - 1; y = i;
        while (x >= 1 && y <= n && s[x] + s[y] == s[i - 1] + s[i])
        {
            cnt++;
            x--; y++;
        }
    }
    fout << cnt << "\n";
    return 0;
}