#include <stdio.h>
#define NMAX 100005
#define ll long long
int n,A[NMAX];
ll rez;
void read()
{
    scanf("%d",&n);
    int i;
    for (i=1; i<=n; i++)
        scanf("%d",&A[i]);
}
void solve()
{
   int i,s,st,dr;
   for (i=1; i<n; i++)
   {
       st=i; dr=i+1;
       s=A[st]+A[dr];
       while (st>1 && dr<n)
           if (A[st-1]+A[dr+1]==s)
                st--,dr++;
           else
                break ;
       rez+=i-st+1;
   }
}
int main()
{
    freopen("numarare.in","r",stdin);
    freopen("numarare.out","w",stdout);
    read();
    solve();
    printf("%lld\n",rez);
    return 0;
}