Scanf.scanf "%s" (fun s ->
    let n = String.length s in
    let rec loop i acc =
        if i = n then acc < 8 else
            loop (i + 1) (acc + if s.[i] = 'x' then 1 else 0)
    in
    print_endline @@ if loop 0 0 then "YES" else "NO"
)