open System

let f (a: float) (b: float) (h: float) (m: float): float =
   let large =
       let minutes = 60. * h + m 
       let rate = minutes / (60. * 12.) 
       let rad = 2. * Math.PI * rate 
       let x = a * cos rad
       let y = a * sin rad 
       (x, y)
   let small = 
       let rate = m / 60.
       let rad = 2.0 * Math.PI * rate 
       let x = b * cos rad 
       let y = b * sin rad 
       (x, y)
   let x = fst large - fst small |> abs 
   let y = snd large - snd small |> abs 
   pown x 2 + pown y 2
   |> sqrt

let l = Console.ReadLine().Split()|> Array.map float 
f l.[0] l.[1] l.[2] l.[3]
|> printfn "%.15f"