#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<ll,ll>;
#define fix(x) fixed << setprecision(x)
#define asc(x) x, vector<x>, greater<x>
#define rep(i, n) for(ll i = 0; i < n; i++)
#define all(x) (x).begin(),(x).end()
template<class T>bool chmin(T&a, const T&b){if(a>b){a=b;return 1;}return 0;}
template<class T>bool chmax(T&a, const T&b){if(a<b){a=b;return 1;}return 0;}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int n;
    cin >> n;
    ll x = -1, cnt = 0, ans = 0;
    rep(i,n+1){
        int a;
        if(i<n) cin >> a;
        else a = -1;
        if(a-x==1) cnt++;
        else{
            ans += cnt * (cnt+1) / 2;
            cnt = 0;
        }
        x = a;
    }
    cout << ans << '\n';
    return 0;
}