(define (main args)
  (let* ([n (read)]
         [k (read)]
         [_ (read-line)]
         [ls (map string->number (string-split (read-line) char-whitespace?))])
    (print
     (let ([sls (sort ls)])
       (apply + (drop (sort (map (lambda (x y) (- x y)) (cdr sls) sls) >) (- k 1))))))
  0)