using static System.Math;
using System.Collections.Generic;
using System.Linq;
using System;

public class Hello
{
    static void Main()
    {
        var n = int.Parse(Console.ReadLine().Trim());
        string[] line = Console.ReadLine().Trim().Split(' ');
        var a = Array.ConvertAll(line, int.Parse);
        getAns(n, a);
    }
    static void getAns(int n, int[] a)
    {
        var b = new List<int>();
        var tc = 0;
        for (int i = 1; i < n; i++)
        {
            if (a[i] - a[i - 1] == 1) tc++;
            else
            {
                if (tc > 0) b.Add(tc);
                tc = 0;
            }
        }
        if (tc > 0) b.Add(tc);
        var ans = 0L;
        foreach (var x in b)
            ans += (long)x * (x + 1) / 2L;
        Console.WriteLine(ans);
    }
}