let () =
  let rec charlist_of_string str n i =
    if i = n then [] else str.[i] :: charlist_of_string str n (i+1) in
  Scanf.scanf "%s\n" @@ fun s ->
  List.iteri (fun i c -> if Char.code c = 97+i then ()
               else print_endline ((Char.escaped (Char.chr (97+i))) ^ "to" ^ (Char.escaped c))) (charlist_of_string s (String.length s) 0)