let f n k = 50 * n + (500 * n / (8 + 2 * k))

let () =
  let a, b = read_line () |>
             Str.split (Str.regexp_string " ") |>
             List.map int_of_string |>
             fun lst -> (List.nth lst 0, List.nth lst 1)
  in
  f a b |> string_of_int |> print_endline