#include <bits/stdc++.h>
using namespace std;
ifstream fin("numarare.in");
ofstream fout("numarare.out");
int n, cnt, a[100005];

/**
      i
1 2 3 4  5   6
j
1 3 6 10 15 21


a b     c      d
a a+b a+b+c a+b+c+d
*/

int main()
{
    int i, j, p, x;
    fin >> n;
    for(i = 1; i <= n; i++)
        fin >> a[i];
    if(n<=3)
    {
        fout<<n-1;
        return 0;
    }
    cnt = n-1;

    for(p = 4; p <= n; p++)
        if(p % 2 == 0)
        {
            j = 1; i = p;
            x = a[j] + a[i];
            while(i > j && x == a[j] + a[i])
            {
                j++;
                i--;
            }
            if(j == i + 1) cnt++;
        }
    fout << cnt << "\n";
    return 0;
}