(define yuki394
  (let*
    (
      (ls (map string->number (string-split (read-line) #\space)))
      (s (apply + ls))
      (t (apply min ls))
      (u (apply max ls))
      (ans (/ (- s t u) 4))
    )
    (format #t "~,2F~%" ans)
  )
)