#include<algorithm>
using namespace std;
#define DIM 100005

long long unsigned sol;
int a[DIM],n;

inline void ext (int x,int y)
{
    int i;
    for(i=0;i<=n;++i)
        if(a[x]+a[y]==a[x-i]+a[y+i] && x-i>0 && y+i<=n)
            ++sol;
        else
            return ;
}
int main ()
{
    freopen("numarare.in","r",stdin);
    freopen("numarare.out","w",stdout);
    int i;
    scanf("%d",&n);
    for(i=1;i<=n;++i)
        scanf("%d",&a[i]);
    for(i=1;i<n;++i)
        ext(i,i+1);
    printf("%llu",sol);
    return 0;
}