#include <bits/stdc++.h>
using namespace std;
int main(){
	ios::sync_with_stdio(0);
	cin.tie(0); cout.tie(0);
	int N; cin >> N;
	int A[200010] = {};
	for(int i = 0; i < N; i++) cin >> A[i];
	long long ans = 0; long long left = 0;
	for(long long i = 1; i <= N; i++){
		if(A[i] == A[i-1] + 1) continue;
		ans += (i - left) * (i - left - 1) / 2;
		left = i;
	}
	cout << ans << "\n";
}