module String = struct
  include String

  let fold_left f init str =
    let n = String.length str - 1 in
    let rec doit i acc =
      if i > n then acc
      else doit (i + 1) (f acc str.[i]) in
    doit 0 init

end

let () =
  read_int () |> ignore;
  let s = read_line () in
  let t = read_line () in
  String.fold_left (fun (i, z) c -> (i + 1, z + if c = t.[i] then 0 else 1)) (0, 0) s
  |> snd |> Printf.printf "%d\n"