QB

module Main

open System

#if DEBUG
open System.IO
Console.SetIn(new StreamReader("..\\..\\in.txt"))
Console.SetOut(new StreamWriter("..\\..\\out.txt"))
#endif

let readInt () =
  let rec parseInput prev sum neg =
    match char (System.Console.Read()) with
    | '-' -> parseInput prev sum true
    | c when System.Char.IsDigit c -> parseInput c (sum * 10 + int c - int '0') neg
    | c when System.Char.IsDigit prev -> if neg then -sum else sum
    | c -> parseInput c sum neg
  parseInput ' ' 0 false

// stuff cutline

[<NoEquality>][<NoComparison>]
type Train = { From : int; Length : int; Velocity : int }

let solve() =
  let rec test() =
    let n, L, S, V = readInt(), readInt(), readInt(), readInt()
    if n <> 0 then
      let cars = Array.init n (fun _ -> readInt(), readInt(), readInt())
      let track = Array.fold (fun sum (x, l, v) -> sum + l + L) S cars |> float
      let stops =
        let rec folder (t : Train) (stops : Train list) =
          match stops with
          | hd :: tl when hd.Velocity >= t.Velocity -> folder { t with Length = t.Length + hd.Length } tl
          | st -> t :: st
        Array.foldBack (fun (x, l, v) stops -> folder { From = x - l - L; Length = l + L; Velocity = v } stops) cars []
        |> folder { From = 0; Length = 0; Velocity = V }
      let answer =
        let folder (time : float, vel : int, head : float) (train : Train) =
          let colAfter = (float train.From - head) / float (vel - train.Velocity)
          let colPos = head + colAfter * float vel
          if colPos > track then (track - head) / float vel, vel, track
          else time + colAfter, train.Velocity, colPos + float train.Length
        let time, vel, pos = List.fold folder (0.0, V + 1, 0.0) stops
        if pos < track then time + (track - pos) / float vel else time
      printfn "%.10f" answer
      test()
  test()

solve()
Console.Out.Flush()