#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>;

// e is only used as retval of empty range query
template<class T, T (*e)()=std::numeric_limits<T>::max>
struct RmQ {
    unsigned int n;
    std::vector<T> a;
    std::vector<std::vector<T>> btable;
    std::vector<unsigned int> ibtable;

    RmQ() {}
    explicit RmQ(std::vector<T> a): a(move(a)), n(a.size()), ibtable(n) {
        preproc_block_RmQ();
        preproc_in_block_RmQ();
    }

    void preproc_block_RmQ() {
        if (n == 0) return;
        const unsigned int m = (n + 31) >> 5; // block count
        const unsigned int k = ceil_pow2(m);
        btable.resize(k + 1);
        for(int i = 0; i <= k; i++) btable[i].resize(m);
        T now = a[n - 1];
        for(int i = n - 1; i >= 0; i--) {
            if (a[i] < now) now = a[i];
            if ((i & 31) == 0) {
                btable[0][i >> 5] = now;
                if (i) {
                    now = a[--i];
                }
            }
        }
        for(unsigned int i = 0; i < k; i++) {
            unsigned int p1 = 0, p2 = 1 << i;
            for(; p2 < m; p1++, p2++) {
                T x = btable[i][p1], y = btable[i][p2];
                btable[i + 1][p1] = (x < y ? x : y);
            }
            for(; p1 < m; p1++) btable[i + 1][p1] = btable[i][p1];
        }
    }

    void preproc_in_block_RmQ() {
        const unsigned int m = (n + 31) >> 5; // block count
        unsigned int st[32];
        for(unsigned int b = 0; b < m; b++) {
            unsigned int s = b << 5, t = std::min((b + 1) << 5, n);
            int top = -1;
            for(unsigned int i = s; i < t; i++) {
                while(top != -1 && !(a[st[top]] < a[i])) top--;
                unsigned int x = 1U << (i & 31);
                if (top != -1) x |= ibtable[st[top]];
                ibtable[i] = x;
                st[++top] = i;
            }
        }
    }

    T operator()(int l, int r) {
        if (l >= r) return e();
        r--; // [l, r]
        const unsigned int bl = l >> 5, ibl = l & 31, br = r >> 5, ibr = r & 31;
        if (bl == br) {
            return a[(bl << 5) | __builtin_ctz(ibtable[r] & (~0U << ibl))];
        } else if (bl + 1 == br) {
            return std::min(a[bl << 5 | __builtin_ctz(ibtable[l | 31] & (~0U << ibl))], a[(br << 5) | __builtin_ctz(ibtable[r])]);
        } else {
            // [bl + 1, br)
            int len = br - bl - 1;
            int k = __lg(len);
            // int k = 31 - __builtin_clz(len);
            return std::min(
                std::min(btable[k][bl + 1], btable[k][br - (1 << k)]),
                std::min(a[bl << 5 | __builtin_ctz(ibtable[l | 31] & (~0U << ibl))], a[(br << 5) | __builtin_ctz(ibtable[r])])
            );
        }
    }

    // excerpt from internal_bit in ACL
    // @param n `0 <= n`
    // @return minimum non-negative `x` s.t. `n <= 2**x`
    int ceil_pow2(int n) {
        int x = 0;
        while ((1U << x) < (unsigned int)(n)) x++;
        return x;
    }
};


} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  VI a(n);
  rep(i, n) cin >> a[i];
  if (n == 1) {
    cout << 1 << '\n';
    return 0;
  }
  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;
  RmQ<int> seg(lcp_array(b, sa));
  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(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(p, q);
    chmin(res, min(i + 1, n - (i + 1)));
    ans += res;
  }
  cout << ans << '\n';
}