let () =
  let rec charlist_of_string str n i =
    if i = n then [] else str.[i] :: charlist_of_string str n (i+1) in
  let rec sum nlst = match nlst with
    | [] -> 0
    | h :: t -> ((int_of_char h) - 48) + sum t in
  let rec solve n i =
    let s = string_of_int n in
    if i > 100 then n
    else solve (sum (charlist_of_string s (String.length s) 0)) (i+1) in
  Scanf.scanf "%d\n" @@ fun n ->
  Printf.printf "%d\n" (solve n 0)