Scanf.scanf "%s" (fun s ->
    let h = Array.make 26 false in
    String.iter (fun c -> h.(int_of_char c - 97) <- true) s;
    let rec chl c s cnt =
        let n = String.length s in
        let rec loop i =
            if i = n then true else
                if s.[i] = c then loop (i + 1) else false
        in
        if loop 0 then cnt else
            let s = String.init (n - 1) (fun i ->
                if s.[i] = c || s.[i + 1] = c then c else s.[i])
            in
            chl c s (cnt + 1)
    in
    let rec loop i acc =
        if i = 26 then acc else
            if h.(i) then loop (i + 1) (min acc (chl (char_of_int (i + 97)) s 0))
                      else loop (i + 1) acc
    in
    loop 0 max_int |> Printf.printf "%d\n"
)