import java.io.PrintWriter
import java.util.*
import kotlin.math.*

fun PrintWriter.solve() {
    val n = nextInt()
    val k = nextInt()
    val a = Array(n) { nextInt() }
    val r = a.sum().toLong()
    var pow = 1L
    var ans = 0L
    for (i in n - 1 downTo 0) {
        ans += a[i] * pow
        ans %= r
        pow *= k
        pow %= r
    }
    println(ans)
}

fun main() {
    val writer = PrintWriter(System.out, false)
    writer.solve()
    writer.flush()
}

// region Scanner
private var st = StringTokenizer("")
private val br = System.`in`.bufferedReader()

fun next(): String {
    while (!st.hasMoreTokens()) st = StringTokenizer(br.readLine())
    return st.nextToken()
}

fun nextInt() = next().toInt()
fun nextLong() = next().toLong()
fun nextLine() = br.readLine()!!
fun nextDouble() = next().toDouble()
// endregion