defmodule Main do
  def main do
    IO.read(:line)
    |> String.trim()
    |> solve
    |> IO.puts()
  end

  defp solve(s) do
    u = s |> String.to_charlist()
    t = u |> length |> div(2)

    cond do
      u |> Enum.slice(0..(t - 1)) ==
          u |> Enum.slice(t..-1) ->
        "YES"

      true ->
        "NO"
    end
  end
end