Scanf.scanf "%s" (fun s ->
    let ten = [| 226; 128; 166 |] in
    let n = String.length s in
    let rec loop i cur acc =
        if i = n then acc else
            let cur = if int_of_char s.[i] = ten.(cur mod 3) then cur + 1 else 0 in
            loop (i + 1) cur (max acc (cur / 3))
    in
    loop 0 0 0 |> Printf.printf "%d\n"
)