#include <bits/stdc++.h>
using namespace std;

struct IoSetup {
	IoSetup() {
		cin.tie(nullptr);
		ios::sync_with_stdio(false);
		cout << fixed << setprecision(10);
		cerr << fixed << setprecision(10);
	}
} iosetup;

template <typename T1, typename T2>
ostream& operator<<(ostream& os, const pair<T1, T2>& p) {
	os << p.first << " " << p.second;
	return os;
}

template <typename T1, typename T2>
istream& operator>>(istream& is, pair<T1, T2>& p) {
	is >> p.first >> p.second;
	return is;
}

template <typename T>
ostream& operator<<(ostream& os, const vector<T>& v) {
	for (int i = 0; i < (int)v.size(); i++) {
		os << v[i] << (i + 1 != v.size() ? " " : "");
	}
	return os;
}

template <typename T>
istream& operator>>(istream& is, vector<T>& v) {
	for (T& in : v) is >> in;
	return is;
}

template <typename T1, typename T2>
inline bool chmax(T1& a, T2 b) {
	return a < b && (a = b, true);
}

template <typename T1, typename T2>
inline bool chmin(T1& a, T2 b) {
	return a > b && (a = b, true);
}

template <typename T = long long>
vector<T> make_v(size_t a) {
	return vector<T>(a);
}

template <typename T, typename... Ts>
auto make_v(size_t a, Ts... ts) {
	return vector<decltype(make_v<T>(ts...))>(a, make_v<T>(ts...));
}

template <typename T, typename V>
typename enable_if<is_class<T>::value == 0>::type fill_v(T& t, const V& v) {
	t = v;
}

template <typename T, typename V>
typename enable_if<is_class<T>::value != 0>::type fill_v(T& t, const V& v) {
	for (auto& e : t) fill_v(e, v);
}
template <class T>
vector<T> read_vec(int n){
	vector<T> v(n);
	for(int i=0;i<n;i++) cin >> v[i];
	return v;
}

template <class T>
vector<vector<T>> read_mat(int h, int w){
	vector<vector<T>> a(h, vector<T>(w));
	for(int i = 0; i < h; i++){
		for(int j = 0; j < w; j++){
			cin >> a[i][j];
		}
	}
	return a;
}
#define rep(i,n) for (int i = 0; i< (n); ++i)
#define repi(i, a, b) for (int i = (a); i < (b); ++i)
#define all(x) (x).begin(), (x).end()
#define fore(i, a) for(auto &i:a)
#define DEBUG(x) cerr << #x << ": "; for (auto _ : x) cerr << _ << " "; cerr << endl;
using ll = long long;
const ll infll = (1LL << 62) - 1;
const int inf = (1 << 30) - 1;
template<class T> using _pq = priority_queue<T, vector<T>, greater<T>>;
template<class T> int LB(vector<T> &v,T a){return lower_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> int UB(vector<T> &v,T a){return upper_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> void So(vector<T> &v) {sort(v.begin(),v.end());}
template<class T> void Sore(vector<T> &v) {sort(v.begin(),v.end(),[](T x,T y){return x>y;});}
bool yneos(bool a,bool upp=false){if(a){cout<<(upp?"YES\n":"Yes\n");}else{cout<<(upp?"NO\n":"No\n");}return a;}
template<class T> T vec_sum(vector<T> &a){T ans=T(0);for(auto &x:a) ans+=x;return ans;}
bool bit(ll x, int k){return((x >> k)&1);}
#include<atcoder/modint>
using namespace atcoder;
using mint = modint998244353;
void solve();

int main(){
	int t=1;
	//cin >> t;
	repi(i, 0, t) solve();
}

void solve(){
  ll n;cin>>n;
	auto a = read_vec<ll>(n);
	if(n == 1){
		cout << 1 << "\n";
		return;
	}
	vector<ll> diff(n-1);
	rep(i, n-1){
		diff[i] = a[i+1]-a[i];
	}
	ll NONE = 209920018;
	vector<ll> S(2*n-3);
	rep(i, n-1){
		S[2*i] = diff[i];
	}
	rep(i, n-2){
		S[2*i+1] = NONE;
	}
	vector<ll> R(2*n-3);
	ll ans = 0;

	int i = 0, j = 1;
	while (i < S.size()) {
		while (i-j >= 0 && i+j < S.size() && S[i-j] == S[i+j]) ++j;
		R[i] = j;
		int k = 1;
		while (i-k >= 0 && k+R[i-k] < j) R[i+k] = R[i-k], ++k;
		i += k; j -= k;
	}
	rep(i, n-1){
		ans += (R[2*i]+1)/2;
	}
	rep(i, n-2){
		ans += R[2*i+1]/2;
	}
	cout << ans+n << "\n";

}