#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using mint = modint998244353;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vvvll = vector<vvll>;
using vmi = vector<mint>;
using vvmi = vector<vmi>;
using vvvmi = vector<vvmi>;
#define all(a) (a).begin(), (a).end()
#define rep2(i, m, n) for (int i = (m); i < (n); ++i)
#define rep(i, n) rep2(i, 0, n)
#define drep2(i, m, n) for (int i = (m)-1; i >= (n); --i)
#define drep(i, n) drep2(i, n, 0)
ll inf = 1e18;
vi manacher(vll &s){
    int len = s.size();
    vi vc(2*len-1, inf);
    rep(i, len)vc[2*i] = s[i];

    int i = 0, j = 0;
        vi res(2*len-1, 0);
        while (i < vc.size()) {
        while (i-j >= 0 && i+j < vc.size() && vc[i-j] == vc[i+j]) ++j;
        res[i] = j;
        int k = 1;
        while (i-k >= 0 && k+res[i-k] < j) res[i+k] = res[i-k], ++k;
        i += k; j -= k;
    }
    rep(i, 2*len-1){
        if(i%2 == 0){
            res[i] = (res[i]+1)/2;
        }else{
            res[i] /= 2;
        }
    }
    return res;
}

int main(){
    int n; cin >> n;
    vll a(n); rep(i, n)cin >> a[i];
    if(n == 1){
        cout << 1 << endl;
        return 0;
    }
    vll b(n-1); rep(i, n-1)b[i] = a[i+1]-a[i];
    vi m = manacher(b);
    ll ans = 0;
    for(auto i : m)ans+=(ll)i;
    cout << ans+(ll)n << endl;
    return 0;
}