let ``No.175 simpleDNA``() =

  let l = stdin.ReadLine() |> int
  let n = stdin.ReadLine() |> int
  let ss= stdin.ReadLine().Split(' ')

  (l - ss.[0].Length)
  |> float
  |> fun num -> System.Math.Pow( 2. ,  num) * float n
  |> stdout.WriteLine

  ()
``No.175 simpleDNA``()