#include <iostream>
#include <cstdint>
#include <vector>

using namespace std;

int main()
{
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	
	int32_t N, i;
	cin >> N;
	vector<int32_t> A(N);
	for (i = 0; i != N; ++i) cin >> A[i];

	int32_t combo = 1;
	int64_t ans = 0;
	for (i = 1; i != N; ++i)
	{
		if (A[i] == A[i - 1] + 1) ++combo;
		else ans += combo * static_cast<int64_t>(combo - 1) / 2, combo = 1;
	}

	cout << ans + combo * static_cast<int64_t>(combo - 1) / 2 << '\n';
	return 0;
}