#include <cstdio>
#define nmax 100010

int n, v[nmax], sol;

int main()
{
    freopen("numarare.in","r",stdin);
    freopen("numarare.out","w",stdout);
    scanf("%d",&n);
    int i, c1, c2;
    for (i=1; i<=n; i++) scanf("%d",&v[i]);
    sol=n-1;
    for (i=1; i<=n; i++)
        for (c1=i-1, c2=i+2; c1>0 && c2<=n; c1--, c2++)
            if (v[c1]+v[c2]==v[i]+v[i+1]) sol++; else break;
    printf("%d",sol);
}