#include <fstream>
using namespace std;
ifstream fi("numarare.in");
ofstream fo("numarare.out");
int n,a[100001],i,st,dr,k;

int main()
{
    fi>>n;
    for(i=1;i<=n;i++) fi>>a[i];

     for(i=1;i<=n-1;i++)
     {st=i;dr=i+1;

    while (st>=1 and dr<=n and a[st]+a[dr]==a[i]+a[i+1])
        {k++;st--;dr++;}
     }
   fo<<k;
    return 0;
}