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();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var n = NN;
        var a = NList;
        WriteLine(Askt(n, a));
    }
    static long Askt(int n, int[] a)
    {
        var left = new int[n][];
        var right = new int[n][];
        for (var i = 0; i < n; ++i)
        {
            left[i] = new int[2001];
            right[i] = new int[2001];
        }
        left[0][a[0]] = 1;
        for (var i = 1; i < n; ++i) for (var j = 0; j < left[i].Length; ++j)
        {
            left[i][j] = left[i - 1][j];
            if (j == a[i]) ++left[i][j];
        }
        right[n - 1][a[n - 1]] = 1;
        for (var i = n - 2; i >= 0; --i) for (var j = 0; j < right[i].Length; ++j)
        {
            right[i][j] = right[i + 1][j];
            if (j == a[i]) ++right[i][j];
        }
        var ans = 0L;
        for (var i = 1; i < n; ++i) for (var j = i + 1; j + 1 < n; ++j)
        {
            if (a[i] <= a[j]) continue;
            var a1 = a[j] - 10;
            var a4 = a[i] + 1;
            if (a1 < 0 || a4 > 2000) continue;
            ans += left[i - 1][a1] * right[j + 1][a4];
        }
        return (ans);
    }
}