#include <iostream>
#include <fstream>

using namespace std;

const int maxi = 100005;
int man[maxi], v[maxi];

ifstream f("numarare.in");
ofstream g("numarare.out");

long long make_man(int (&v)[maxi], int n)
{
    int r = 0, c = 0;
    long long ans = 0;
    for (int i = 1; i < n; ++ i)
    {
        int op = 2 * c - i;
        if (i > r || man[op] >= r - i)
        {
            if (i > r)
                r = i;
            int k = r + 1;
            int sum = v[i] + v[i + 1];
            while (k <= n && (2 * i - k + 1 > 0) && (v[k] + v [2 * i - k + 1] == sum))
                k ++;
            k --;
            man[i] = k - i;
            if (k > r)
            {
                c = i;
                r = k;
            }
        }
        else
            man[i] = man[op];
        ans += man[i];
    }
    return ans;
}
int main()
{
    int n;
    f >> n;
    for (int i = 1; i <= n; ++ i)
        f >> v[i];
    g <<  make_man(v, n);
}