import scala.annotation.tailrec
import scala.io.StdIn.*
import scala.math.*

object ModInt:
  opaque type ModInt = Long
  extension (value: Long)
    inline def asModInt(using inline mod: Int): ModInt =  value % mod
  extension (value: Int)
    inline def asModInt(using inline mod: Int): ModInt = value % mod
  trait Converter[T]:
    inline def convert(value: T)(using inline mod: Int): ModInt
  inline given Converter[Int] with
    override inline def convert(value: Int)(using inline mod: Int) = value.asModInt
  inline given Converter[Long] with
    override inline def convert(value: Long)(using inline mod: Int) = value.asModInt
  inline given Converter[ModInt] with
    override inline def convert(value: ModInt)(using inline mod: Int) = value
  extension (modInt: ModInt)
    inline def asLong(using inline mod: Int): Long = (modInt + mod) % mod
    inline def inverse(using inline mod: Int): ModInt = modInt.powMod(mod - 2)
    inline def powMod(exp: Long)(using inline mod: Int): ModInt =
      var result = 1L
      var base = modInt
      var e = exp
      while e > 0 do
        if (e & 1) == 1 then
          result = result * base % mod
        base = base * base % mod
        e >>= 1
      result
    inline def powMod(exp: Int)(using inline mod: Int): ModInt = powMod(exp.toLong)
  extension [L: Converter, R: Converter] (left: L)
    inline def +(right: R)(using inline mod: Int): ModInt = (summon[Converter[L]].convert(left) + summon[Converter[R]].convert(right)).asModInt
    inline def -(right: R)(using inline mod: Int): ModInt = (summon[Converter[L]].convert(left) - summon[Converter[R]].convert(right)).asModInt
    inline def *(right: R)(using inline mod: Int): ModInt = (summon[Converter[L]].convert(left) * summon[Converter[R]].convert(right)).asModInt
    inline def /(right: R)(using inline mod: Int): ModInt = (summon[Converter[L]].convert(left) * summon[Converter[R]].convert(right).inverse).asModInt

@main def main =
  import ModInt.*
  inline given mod: Int = 1000000007
  val Array(n, k) = readLine().split(' ').map(_.toInt)
  val a = readLine().split(' ').map(_.toInt)
  val combination = Array.fill(n){1.asModInt}
  for i <- 1 until n do
    combination(i) = combination(i - 1) * (k + i) / i
  var result = 0.asModInt
  for
    i <- 0 until n
  do
    val current = a(i) * combination(i) * combination(n - i - 1)
    result += current
  println(result.asLong)