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

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static void Main()
    {
        var n = NN;
        var a = NList;
        var res = 0L;
        var cnt = 1L;
        for (var i = 0; i < a.Length; ++i)
        {
            if (i + 1 < a.Length && a[i + 1] - a[i] == 1)
            {
                ++cnt;
            }
            else
            {
                res += cnt * (cnt - 1) / 2;
                cnt = 1;
            }
        }
        WriteLine(res);
    }
}