#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic warning "-Wunused-function"
using namespace std;
using namespace atcoder;
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; i--)
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; } else return false; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return true; } else return false; }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  VI a(n);
  rep(i, n) cin >> a[i];
  VI b(2 * (n - 1));
  rep(i, n - 1) b[i] = a[i+1] - a[i];
  rep(i, n - 1) b[n-1+i] = -(a[n-1-(i+1)] - a[n-1-i]);
  VI sa = suffix_array(b);
  VI inv(2 * (n - 1));
  rep(i, 2 * (n - 1)) inv[sa[i]] = i;
  VI lcp = lcp_array(b, sa);
  segtree<int, [](int x, int y) { return min(x, y); }, []() { return 1001001001; }> seg(lcp);
  ll ans = 0;
  rep(i, n) {
    if (i == 0 || i == n - 1) {
      ans++;
      continue;
    }
    int p = inv[i], q = inv[n-1+n-1-i];
    if (p > q) swap(p, q);
    int res = seg.prod(p, q) + 1;
    chmin(res, min(i + 1, n - i));
    ans += res;
  }
  rep(i, n - 1) {
    if (i == 0 || i == n - 2) {
      ans++;
      continue;
    }
    int p = inv[i], q = inv[n-1+n-1-(i+1)];
    if (p > q) swap(p, q);
    int res = seg.prod(p, q);
    chmin(res, min(i + 1, n - (i + 1)));
    ans += res;
  }
  cout << ans << '\n';
}