open System


let solve a b c d =
    let isEnable a b c d =
        let j1 = a * c <= b
        let j2 = a + b <= d
        j1 && j2
    [ for iA in 0 .. a do 
      for iB in 0 .. b do
      if isEnable iA iB c d then yield iA ]
    |> Seq.max

let a, b, c, d =
    let t = Console.ReadLine().Split() |> Array.map int
    t.[0], t.[1], t.[2], t.[3]

solve a b c d
|> Console.WriteLine