let alph = Array.make 26 0 ;;

let insert c =
  let code = Char.code c in
  let x = (code - 97) in
  if 97 <= code && code <= 122 then
    begin alph.(x) <- alph.(x) + 1 end ;;

let rec f () =
  try
    let s = read_line() in
    String.iter (fun x -> Char.lowercase x |> insert) s;
    f()
  with
    End_of_file ->
    Array.iteri (fun i x -> print_char (Char.chr (i + 97)); print_string " : "; print_endline (string_of_int x)) alph;;

f();;
