let inp : unit -> string = fun () -> 
  input_line stdin

  
let () =
  let s = inp () in
  let rec count n l =
    if n = 4 then
      l
    else
      if List.mem s.[n] l then
        count (n + 1) l
      else
        count (n + 1) (s.[n] :: l)
  in
  let c = List.length (count 0 []) in
  let n =
    let rec f n m =
          if n = 4 then
            m
          else
            if s.[n] = s.[0] then
              f (n + 1) (m + 1)
            else
              f (n + 1) m in
    f 0 0
  in
  if c = 2 && n = 2 then
    print_endline "Yes"
  else
    print_endline "No"
