using System.Linq;
using System;

public class Hello
{
    static void Main()
    {
        string[] line = Console.ReadLine().Trim().Split(' ');
        var n = int.Parse(line[0]);
        var k = int.Parse(line[1]);
        line = Console.ReadLine().Trim().Split(' ');
        var a = Array.ConvertAll(line, int.Parse);
        getAns(n, k, a);
    }
    static void getAns(int n, int k, int[] a)
    {
        var asum = a.Sum();
        Array.Reverse(a);
        var p = 1L;
        var ans = 0L;
        for (int i = 0; i < n; i++)
        {
            ans += a[i] * (p % asum);
            ans %= asum;
            p *= k;
        }
        Console.WriteLine(ans);
    }
}