using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;
class Program
{
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var n = int.Parse(ReadLine());
        var a = NList;

        var count = new int[9];
        foreach (var ai in a) ++count[ai];
        var ans = 0L;
        for (var i = 1; i <= 8; ++i) for (var j = 1; j <= 8; ++j)
        {
            ans += (long)Math.Pow(i, j) * count[i] * count[j];
        }
        WriteLine(ans);
    }
}