#ifdef ONLINE_JUDGE
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#endif
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
#define rep(i, n) for (ll i = 0; i < (ll)(n); i++)
#define rrep(i,start,end) for (ll i = start;i >= (ll)(end);i--)
#define repn(i,end) for(ll i = 0; i <= (ll)(end); i++)
#define reps(i,start,end) for(ll i = start; i < (ll)(end); i++)
#define repsn(i,start,end) for(ll i = start; i <= (ll)(end); i++)
#define each(p,a) for(auto &p:a)
typedef vector<ll> vll;
typedef vector<pair<ll ,ll>> vpll;
typedef vector<vector<pair<ll ,ll>>> vvpll;
typedef vector<vector<ll>> vvll;
typedef vector<vector<vector<ll>>> vvvll;
typedef set<ll> sll;
typedef map<ll , ll> mpll;
typedef pair<ll ,ll> pll;
typedef tuple<ll , ll , ll> tpl3;
typedef tuple<ll , ll , ll , ll> tpl4;
typedef tuple<ll , ll , ll , ll , ll> tpl5;
typedef tuple<ll , ll , ll , ll , ll , ll> tpl6;
#define LL(...) ll __VA_ARGS__; input(__VA_ARGS__)
#define LD(...) ld __VA_ARGS__; input(__VA_ARGS__)
#define Str(...) string __VA_ARGS__; input(__VA_ARGS__)
#define Ch(...) char __VA_ARGS__; input(__VA_ARGS__)
#define all(a)  (a).begin(),(a).end()
#define UNIQUE(v) v.erase( unique(v.begin(), v.end()), v.end() );
#define sz(x) (ll)x.size()
// << std::fixed << std::setprecision(10)
const ll INF = 1LL << 60;
const ld EPS = 1e-9;
 
ll lceil(ll a,ll b){if(a%b==0){return a/b;}if(a>=0){return (a/b)+1;}else{return -((-a)/b);}}
ll lfloor(ll a,ll b){if(a%b==0){return a/b;}if(a>=0){return (a/b);}else{return -((-a)/b)-1;}}
inline ll positive_mod(ll a,ll m){return (a % m + m)%m;}
inline ll popcnt(ull a){ return __builtin_popcountll(a);}
//0indexed
inline ll topbit(ll a){assert(a != 0);return 63 - __builtin_clzll(a);}
inline ll smlbit(ll a){assert(a != 0);return __builtin_ctzll(a);}
template<class T> bool chmin(T& a, T b){if(a > b){a = b;return true;}return false;}
template<class T> bool chmax(T& a, T b){if(a < b){a = b;return true;}return false;}
template<typename T> std::istream &operator>>(std::istream&is,std::vector<T>&v){for(T &in:v){is>>in;}return is;}
template<typename T> std::ostream &operator<<(std::ostream&os,const std::vector<T>&v){for(auto it=std::begin(v);it!=std::end(v);){os<<*it<<((++it)!=std::end(v)?" ":"");}return os;}
template<typename T1, typename T2>std::ostream &operator<< (std::ostream &os, std::pair<T1,T2> p){os << "{" << p.first << "," << p.second << "}";return os;}
template<class... T>void input(T&... a){(cin >> ... >> a);}
void print(){cout << endl;}
template<class T, class... Ts>void print(const T& a, const Ts&... b){cout << a;((cout << ' ' << b), ...);cout << endl;}
template<class T> void pspace(const T& a){ cout << a << ' ';}
void perr(){cerr << endl;}
template<class T, class... Ts>void perr(const T& a, const Ts&... b){cerr << a;((cerr << ' ' << b), ...);cerr << endl;}
void yes(bool i = true){ return print(i?"yes":"no"); }
void Yes(bool i = true){ return print(i?"Yes":"No"); }
void YES(bool i = true){ return print(i?"YES":"NO"); }
template <class T> vector<T> &operator++(vector<T> &v) {for(auto &e : v) e++;return v;}
template <class T> vector<T> operator++(vector<T> &v, signed) {auto res = v;for(auto &e : v) e++;return res;}
template <class T> vector<T> &operator--(vector<T> &v) {for(auto &e : v) e--;return v;}
template <class T> vector<T> operator--(vector<T> &v, signed) {auto res = v;for(auto &e : v) e--;return res;}
//grid探索用
vector<ll> _ta = {0,0,1,-1,1,1,-1,-1};
vector<ll> _yo = {1,-1,0,0,1,-1,1,-1};
bool isin(ll now_i,ll now_j,ll h,ll w){return (0<=now_i && now_i < h && 0 <= now_j && now_j < w);}
  
ll lpow(ll x,ll n){ll ans = 1;while(n >0){if(n & 1)ans *= x;x *= x;n >>= 1;}return ans;}
ll Modlpow(ll x,ll n,ll m){ll ans = 1;ll a = x%m;while(n >0){if(n & 1){ans *= a;ans%= m;}a *= a;a %= m;n >>= 1;}return ans;} 
const ll MOD9 = 998244353LL;
const ll MOD10 = 1000000007LL;

//参考 https://drken1215.hatenablog.com/entry/2019/03/12/135500
//https://qiita.com/keymoon/items/11fac5627672a6d6a9f6
//verify https://atcoder.jp/contests/abc430/submissions/70648380

namespace Hash{
  const ull MASK30 = (1UL << 30) - 1;
  const ull MASK31 = (1UL << 31) - 1;
  const ull MOD = (1UL << 61) - 1;
  const ull MASK61 = MOD;
  const ull POSITIVIZER = MOD * 4;
  const ull base = 2*lpow(10,9)+2;
  //mod 2^61-1を計算する関数
  ull CalcMod(ull x)
  {
      ull xu = x >> 61;
      ull xd = x & MASK61;
      ull res = xu + xd;
      if (res >= MOD) res -= MOD;
      return res;
  }
  //a*b mod 2^61-1を返す関数(最後にModを取る)
  ull Mul(ull a, ull b)
  {
      ull au = a >> 31;
      ull ad = a & MASK31;
      ull bu = b >> 31;
      ull bd = b & MASK31;
      ull mid = ad * bu + au * bd;
      ull midu = mid >> 30;
      ull midd = mid & MASK30;
      return CalcMod(au * bu * 2 + midu + (midd << 31) + ad * bd);
  }
  
  //2^61 -1 で割る時のpow計算
  
  ull SuperMODpow(ll x,ll n){
    // MOD = (1UL << 61) - 1;,Mul,CalcMod必要
    ull ans = 1;
    ull a = x;
    while(n> 0){
      if(n & 1){
        ans = Mul(ans,a);
      }
      a = Mul(a,a);
      n>>=1;
    }
    return ans;
  }

  // ロリハのマージ用
  // S + T をマージするとき
  // top = hash(S) , btm = hash(T), btmlen = |T| 
  ull merge(ull top,ull btm,ll btmlen){
    return CalcMod(Mul(top,SuperMODpow(base,btmlen)) + btm);
  }
}

struct RollingHash{
  vector<ull> hash;
  vector<ull> pre;

  RollingHash(){}

  RollingHash(const vector<int> &_s){
    init(_s);
  }

  void init(const vector<int> &_s){
    ll n = _s.size();
    hash.assign(n+1,0);
    rep(i,n){
      hash[i + 1] = Hash::CalcMod((Hash::Mul(hash[i],Hash::base) + _s[i]));
      pre.push_back(Hash::SuperMODpow(Hash::base,i));
    }
    pre.push_back(Hash::SuperMODpow(Hash::base,n));
  }

  //[l,r)のハッシュを返す
  inline ull get(ll l,ll r){
    return Hash::CalcMod(hash[r]+ Hash::POSITIVIZER - Hash::Mul(hash[l],pre[r-l]));
  }
};
 
int main(){
  ios::sync_with_stdio(false);cin.tie(nullptr);
  LL(n);
  vector<int> a(n);cin >> a;
  vector<int> b(n-1);
  int btm = lpow(10,9);
  rep(i,n-1){
    b[i] = a[i+1]-a[i]+btm;
  }
  vector<int> c = b;
  reverse(all(c));
  RollingHash rh(b),rrh(c);
  ll ans = 0;
  auto rclc = [&](int l,int r){
    //[l,r)の反転
    return rrh.get(n-2-(r-1),n-2-(l-1));
  };
  rep(i,n){
    //iを中心
    {
      int ng = min(i+1,n-i);//条件を満たさない値
      int ok = 0;//条件を満たす値
      auto f = [&](int mid)->bool {
        //mid個
        ull left = rh.get(i-mid,i);
        ull right = rclc(i,i+mid);
        return left == right;
      };
      while(abs(ok-ng) > 1){
        int mid = (ok + ng)/2;
        if(f(mid)){
          ok = mid;
        }else{
          ng = mid;
        }
      }
      ans += ok+1;
    }
    //(i,i+1)を中心
    if(i+1 < n){
      int ok = 0;//条件を満たす値
      int ng = min(i+1,n-(i+1));//条件を満たさない値
      auto f = [&](int mid)->bool {
        ull left = rh.get(i-mid,i);
        ull right = rclc(i+1,i+1+mid);
        return left == right;
      };
      while(abs(ok-ng) > 1){
        int mid = (ok + ng)/2;
        if(f(mid)){
          ok = mid;
        }else{
          ng = mid;
        }
      }
      ans += ok+1;
    }
  }
  cout << ans << endl;
}