let A,B,X,Y = let t = stdin.ReadLine().Split()
                      |> Array.map(float)
              t.[0],t.[1],t.[2],t.[3]

let ajustA = 
    let t = B/A
    if X*t <= Y then Some(X*(1.0+t))
    else             None

let ajustB =
    let t = A/B
    if Y*t <= X then Some(Y*(1.0+t))
    else             None                        

match ajustA,ajustB with
| Some(a),Some(b) -> max a b 
| Some(a),None    -> a 
| None   ,Some(b) -> b 
| None   ,None    -> failwith "error"
|> printfn "%f"