Scanf.scanf "%d %d" (fun n l ->
    let z = 998244353 in
    let ( *@) a b = (a * b) mod z in

    let modpow a b =
        let rec loop r i acc =
            if i = 0 then acc else loop (r *@ r) (i lsr 1) (if i land 1 = 0 then acc else acc *@ r)
        in
        loop a b 1
    in

    let a = (n + l - 1) / l in

    Printf.printf "%d\n" @@ (modpow 2 a + z - 1) mod z
)