#include <bits/stdc++.h>

using namespace std;

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

int n,a[100005],cnt;

int main()
{
    int i,st,dr,sum,g;
    fin>>n;
    for(i=1;i<=n;i++)
        fin>>a[i];
    for(i=1;i<n;i++)
    {
        st=i;
        dr=i+1;
        sum=a[st]+a[dr];
        while(st>0&&dr<=n&&a[st]+a[dr]==sum)
        {
            cnt++;
            st--;
            dr++;
        }
    }
    fout<<cnt<<"\n";
    return 0;
}