#include <cstdio>
#include <cstring>
#include <algorithm>
#define maxN 100002
using namespace std;
int n, i, j, v[maxN], s[maxN], sol;
void read()
{
    freopen("numarare.in", "r", stdin);
    scanf("%d", &n);
    for (i = 1; i <= n; ++ i)
    {
        scanf("%d", &v[i]);
        if (i > 1)
            v[i - 1] -= v[i];
    }
}
void solve()
{
    int pos = 1;
    -- n;
    for (i = 1; i <= n; ++ i)
    {
        if (i < pos + s[pos])
            s[i] = min(s[2 * pos - i], s[pos] - i + pos);
        if (i + s[i] >= pos + s[pos])
        {
            pos = i;
            while (i - s[i] - 1 >= 1 && i + s[i] + 1 <= n &&
                    v[i - s[i] - 1] == v[i + s[i] + 1])
                ++ s[i];
        }
    }
}
void write()
{
    freopen("numarare.out", "w", stdout);
    sol = n;
    for (i = 1; i <= n; ++ i)
        sol += s[i];
    printf("%d", sol);
}
int main()
{
    read();
    solve();
    write();
}