let ``No.804 野菜が苦手``() =

  let a, b, c, d = 
    stdin.ReadLine().Split(' ')
    |> Array.map (int)
    |> fun args -> args.[0] , args.[1], args.[2], args.[3]

  let rec loop v m pw pc =
 
    if v > a || m > b || (pc < v + v * pw)
      then loop (v-1) ((v-1)*pw) pw pc
      else v

  loop a (a*c) c d
  |> stdout.WriteLine
  ()
``No.804 野菜が苦手``()