#include <bits/stdc++.h>
using namespace std;

long long n, b, m;
long long a[200000];

int main() {
	cin >> n;

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

		if (i > 0) {
			if (a[i] != a[i - 1] + 1) {
				m += (i - b) * (i - b - 1) / 2;
				b = i;
			}
		}
	}

	if (b != n - 1)
		m += (n - b) * (n - b - 1) / 2;

	cout << m << endl;
}