import sequtils, strutils
proc printf(str: cstring) {.header: "<stdio.h>", importc: "printf", varargs.}
let
  a: seq[int] = stdin.readline.split.map(parseInt)
  x: float = a[2].float * (1.0 + a[1] / a[0])
  y: float = a[3].float * (1.0 + a[0] / a[1])
  ans: float = min(x, y)
printf("%.8f", ans)