(define (ave10 arr)
  (define len (length arr))
  (div (* 10 (fold + 0 arr)) len))

(define (solve k arr)
  (define len (length arr))
  (define max (ave10 (take-right arr 1)))
  (define min (ave10 (take arr 1)))
  (div (+ (- max min) 9) 10))

(let* ((n (string->number (read-line)))
       (k (string->number (read-line)))
       (arr (map (lambda (_) (string->number (read-line))) (iota n))))
  (print (solve k (sort arr))))