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 c = NList;
        var (n, k) = (c[0], c[1]);
        var a = NList;
        var mod = a.Sum();
        var mul = 1L;
        var ans = 0L;
        for (var i = 0; i < n; ++i)
        {
            ans = (ans + a[n - i - 1] * mul % mod) % mod;
            mul = mul * k % mod;
        }
        WriteLine(ans);
    }
}