typedef long long ll;
typedef long double ld;
#include <bits/stdc++.h>
using namespace std;
#define int long long

signed main(){
    ll n;
    std::cin >> n;
    vector<ll> a(n),b;
    for (int i = 0; i < n; i++) {
        std::cin >> a[i];
        if(i>0){
            b.push_back(a[i]-a[i-1]);
        }
    }
    ll ans = 0;
    ll now  = 0;
    for (int i = 0; i < n-1; i++) {
        if(b[i]==1){
            now++;
        }else{
            ans += now*(now+1)/2;
            now = 0;
        }
    }
    ans += now*(now+1)/2;
    std::cout << ans << std::endl;
}