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 int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var n = NN;
        var m = new int[n];
        for (var i = 0; i < n; ++i) m[i] = NN - 1;
        var ft = new AtCoder.FenwickTree<int>(n);
        var ans = 0L;
        for (var i = n - 1; i >= 0; --i)
        {
            if (m[i] > 0) ans += ft.Sum(m[i]);
            ft.Add(m[i], 1);
        }
        WriteLine(ans);
    }
}