defmodule Main do
  def input, do: IO.read(:line) |> String.trim
  def ii, do: input() |> String.to_integer
  def li, do: input() |> String.split |> Enum.map(&String.to_integer/1)
  def yn(b), do: IO.puts (if b, do: "Yes", else: "No")

  def main do
    a = Enum.sort(li())

    hd = Enum.at(a, 0)
    ans = if Enum.to_list(hd..hd+3) == a, do: "Yes", else: "No"
    IO.puts ans
  end
end