wallpaper.ex

defmodule Wallpaper do
  
  @spec wallpaper(number, number, number) :: String.t
  
  def wallpaper(l, w, h) do
    case (( ( l * h ) + (w * h) )* 2 * 1.15 ) / 5.2 |> Float.ceil do
      0.0 -> "zero"
      1.0 -> "one"
      2.0 -> "two"
      3.0 -> "three"
      4.0 -> "four"
      5.0 -> "five"
      6.0 -> "six"
      7.0 -> "seven"
      8.0 -> "eight"
      9.0 -> "nine"
      10.0 -> "ten"
      11.0 -> "eleven"
      12.0 -> "twelve"
      13.0 -> "thirteen"
      14.0 -> "fourteen"
      15.0 -> "fifteen"
      16.0 -> "sixteen"
      17.0 -> "seventeen"
      18.0 -> "eighteen"
      19.0 -> "nineteen"
      _ -> "twenty"
    end
    
  end
  
end