defmodule Main do
  def main do
    1..2
    |> Enum.map(fn _ ->
      IO.read(:line)
      |> String.split()
      |> Enum.map(&String.to_integer/1)
    end)
    |> solve
    |> IO.puts()
  end

  defp solve([[_, a], x]) do
    cond do
      (x |> Enum.sum()) / (x |> length) == a -> "YES"
      true -> "NO"
    end
  end
end