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

int main()
{
    int N;
    cin >> N;
    vector<int> A(N);
    for (int i = 0; i < N; i++)
    {
        cin >> A[i];
    }
    long long size = 0;
    long long ans = 0;
    for (int i = 1; i < N; i++)
    {
        if (A[i - 1] == A[i] - 1)
        {
            size++;
        }
        else
        {
            if (size >= 1)
            {
                ans += (size * size + size) / 2;
            }
            size = 0;
        }
    }
    if (size >= 1)
    {
        ans += (size * size + size) / 2;
    }
    cout << ans;
}