#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>
#include <array>
#include <atomic>
#include <chrono>
#include <condition_variable>
#include <forward_list>
#include <future>
#include <initializer_list>
#include <mutex>
#include <random>
#include <ratio>
#include <regex>
#include <scoped_allocator>
#include <system_error>
#include <thread>
#include <tuple>
#include <typeindex>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
#define whole(v) (v).begin(),(v).end()
#define rwhole(v) (v).rbegin(),(v).rend()
#define press(v) (v).erase(unique(whole(v)),(v).end())
#define Yes cout<<"Yes"<<endl; return 0
#define No cout<<"No"<<endl; return 0
#define vint vector<int>
#define vll vector<ll>
#define vpint vector<pair<int,int>>
#define vvint vector<vector<int>>
#define vvll vector<vector<ll>>
#define pqint priority_queue<int>
#define pqpint priority_queue<pair<int,int>>
#define rpqint priority_queue<int,vector<int>,greater<int>>
#define rpqpint priority_queue<pair<int,int>,vector<pair<int,int>>,greater<pair<int,int>>>
using namespace std;
using ll = long long;
int mod107 = 1000000007, mod998 = 998244353;
string alphabet = "abcdefghijklmnopqrstuvwxyz", ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

//(a,b)と(c,d)の距離
double pyth(ll a, ll b, ll c, ll d) {
    double l = sqrt((a - c) * (a - c) + (b - d) * (b - d));
    return l;
}

//aのb乗をmで割った余り(a,bは非負整数,mは自然数)
int power(ll a, ll b, int m) {
    int k = 0, ans = 1;
    vector<ll> v(100);
    v[0] = a;
    for (int i = 1; i < 100; i++)
        v[i] = v[i - 1] * v[i - 1] % m;
    while (b > 0) {
        if (b % 2)
            ans = ans * v[k] % m;
        k++; b /= 2;
    }
    return ans;
}

//素数判定 O(sqrt(n))
bool prime_judge(ll n) {
    for (int i = 2; i <= sqrt(n); i++) {
        if (n % i == 0) {
            return false;
        }
    }
    return true;
}

int main() {
    int n;
    cin >> n;
    vint a(n);

    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }

    int num = 1, ans = 0;

    for (int i = 0; i < n - 1; i++) {

        if (a[i] + 1 == a[i + 1]) {
            num++;
        }

        else {
            ans += num * (num - 1) / 2;
            num = 1;
        }

        if (i == n - 2) {
            ans += num * (num - 1) / 2;
        }
    }

    cout << ans << endl;
}