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

int main()
{
	int64_t n;
	cin >> n;
	vector<int64_t> a(n);
	for(int64_t i = 0; i < n; i++) cin >> a[i];
	
	int64_t v = a[0];
	int64_t ans = 0;
	int64_t cnt = 1;
	for(int64_t i = 1; i < n; i++)
	{
		if(v + 1 == a[i]) cnt++;
		else
		{
			ans += cnt * (cnt - 1) / 2;
			cnt = 1;
		}
		v = a[i];
	}
	ans += cnt * (cnt - 1) / 2;
	cout << ans << endl;
	return 0;
}