#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, s, e) for (int i = (int)s; i < (int)e; i++)

int main() {
    cin.tie(nullptr);
    
    int N;
    cin >> N;
    
    vector<int> A(N);
    rep(i, 0, N) cin >> A[i];
    
    vector<int> d(N - 1);
    rep(i, 0, N - 1) d[i] = A[i + 1] - A[i];
    
    ll ans = 0;
    ll cnt = 0;
    rep(i, 0, N - 1) {
        if (d[i] == 1) cnt++;
        else {
            ans += (cnt + 1) * cnt / 2;
            cnt = 0;
        }
    }
    if (cnt != 0) ans += (cnt + 1) * cnt / 2;
    
    cout << ans << '\n';
}