(eval-when (:compile-toplevel :load-toplevel :execute)
  (sb-int:defconstant-eqx OPT
    #+swank '(optimize (speed 3) (safety 2))
    #-swank '(optimize (speed 3) (safety 0) (debug 0))
    #'equal)
  #+swank (ql:quickload '(:cl-debug-print :fiveam) :silent t)
  #-swank (set-dispatch-macro-character
           ;; enclose the form with VALUES to avoid being captured by LOOP macro
           #\# #\> (lambda (s c p) (declare (ignore c p)) `(values ,(read s nil nil t)))))
#+swank (cl-syntax:use-syntax cl-debug-print:debug-print-syntax)
#-swank (disable-debugger) ; for CS Academy

;; BEGIN_INSERTED_CONTENTS
(macrolet ((def (name fname)
             `(define-modify-macro ,name (new-value) ,fname)))
  (def minf min)
  (def maxf max)
  (def mulf *)
  (def divf /)
  (def iorf logior)
  (def xorf logxor)
  (def andf logand))

(defmacro dbg (&rest forms)
  #+swank
  (if (= (length forms) 1)
      `(format *error-output* "~A => ~A~%" ',(car forms) ,(car forms))
      `(format *error-output* "~A => ~A~%" ',forms `(,,@forms)))
  #-swank (declare (ignore forms)))

(defmacro define-int-types (&rest bits)
  `(progn
     ,@(mapcar (lambda (b) `(deftype ,(intern (format nil "UINT~A" b)) () '(unsigned-byte ,b))) bits)
     ,@(mapcar (lambda (b) `(deftype ,(intern (format nil "INT~A" b)) () '(signed-byte ,b))) bits)))
(define-int-types 2 4 7 8 15 16 31 32 62 63 64)

(declaim (inline println))
(defun println (obj &optional (stream *standard-output*))
  (let ((*read-default-float-format* 'double-float))
    (prog1 (princ obj stream) (terpri stream))))

(defconstant +mod+ 1000000007)

;;;
;;; Body
;;;
(defconstant +inf+ #xffffffff)
(defun max2 (list)
  (let ((max -1)
        (max2 -1))
    (assert (cdr list))
    (dolist (x list)
      (cond ((>= x max)
             (setq max2 max max x))
            ((>= x max2)
             (setq max2 x))))
    (values max max2)))

(defun main ()
  (let* ((n (read))
         (k (read))
         (edges (make-array (- n 1) :element-type 'list))
         (graph (make-array n :element-type 'list :initial-element nil)))
    (dotimes (i (- n 1))
      (let ((a (- (read) 1))
            (b (- (read) 1)))
        (setf (aref edges i) (cons a b))
        (push a (aref graph b))
        (push b (aref graph a))))
    (let ((k/2 (floor k 2))
          (res +inf+)
          (dists (make-array n :element-type 'uint32)))
      (labels ((fill-dists (v parent depth)
                 (setf (aref dists v) depth)
                 (dolist (child (aref graph v))
                   (unless (= child parent)
                     (fill-dists child v (+ depth 1)))))
               (get-max-depth (v parent)
                 (let ((res (aref dists v)))
                   (dolist (child (aref graph v))
                     (unless (= child parent)
                       (maxf res (get-max-depth child v))))
                   res)))
        (if (evenp k)
            (dotimes (root n)
              (when (cdr (aref graph root))
                (fill dists +inf+)
                (fill-dists root -1 0)
                (let* ((branch-depths (loop for child in (aref graph root)
                                            collect (get-max-depth child root))))
                  (dbg root dists branch-depths)
                  (multiple-value-bind (max max2) (max2 branch-depths)
                    (dbg max max2)
                    (when (>= max2 k/2)
                      (minf res (count-if (lambda (d) (> d k/2)) dists)))))))
            (loop
              for (r1 . r2) across edges
              when (and (car (aref graph r1))
                        (car (aref graph r2)))
              do (fill dists +inf+)
                 (fill-dists r1 r2 0)
                 (fill-dists r2 r1 0)
                 #>dists
                 (let* ((branch-depths1 (cons 0 (loop for child in (aref graph r1)
                                                      unless (= child r2)
                                                      collect (get-max-depth child r1))))
                        (branch-depths2 (cons 0 (loop for child in (aref graph r2)
                                                      unless (= child r1)
                                                      collect (get-max-depth child r2)))))
                   (dbg branch-depths1 branch-depths2)
                   (let ((max-depth1 (reduce #'max branch-depths1))
                         (max-depth2 (reduce #'max branch-depths2)))
                     (when (>= (min max-depth1 max-depth2) k/2)
                       (minf res (count-if (lambda (x) (> x k/2)) dists))))))))
      (println
       (if (= res +inf+)
           0
           res)))))

#-swank (main)

;;;
;;; Test and benchmark
;;;

#+swank
(defun io-equal (in-string out-string &key (function #'main) (test #'equal))
  "Passes IN-STRING to *STANDARD-INPUT*, executes FUNCTION, and returns true if
the string output to *STANDARD-OUTPUT* is equal to OUT-STRING."
  (labels ((ensure-last-lf (s)
             (if (eql (uiop:last-char s) #\Linefeed)
                 s
                 (uiop:strcat s uiop:+lf+))))
    (funcall test
             (ensure-last-lf out-string)
             (with-output-to-string (out)
               (let ((*standard-output* out))
                 (with-input-from-string (*standard-input* (ensure-last-lf in-string))
                   (funcall function)))))))

#+swank
(defun get-clipbrd ()
  (with-output-to-string (out)
    (run-program "powershell.exe" '("-Command" "Get-Clipboard") :output out :search t)))

#+swank (defparameter *this-pathname* (uiop:current-lisp-file-pathname))
#+swank (defparameter *dat-pathname* (uiop:merge-pathnames* "test.dat" *this-pathname*))

#+swank
(defun run (&optional thing (out *standard-output*))
  "THING := null | string | symbol | pathname

null: run #'MAIN using the text on clipboard as input.
string: run #'MAIN using the string as input.
symbol: alias of FIVEAM:RUN!.
pathname: run #'MAIN using the text file as input."
  (let ((*standard-output* out))
    (etypecase thing
      (null
       (with-input-from-string (*standard-input* (delete #\Return (get-clipbrd)))
         (main)))
      (string
       (with-input-from-string (*standard-input* (delete #\Return thing))
         (main)))
      (symbol (5am:run! thing))
      (pathname
       (with-open-file (*standard-input* thing)
         (main))))))

#+swank
(defun gen-dat ()
  (uiop:with-output-file (out *dat-pathname* :if-exists :supersede)
    (format out "")))

#+swank
(defun bench (&optional (out (make-broadcast-stream)))
  (time (run *dat-pathname* out)))

;; To run: (5am:run! :sample)
#+swank
(it.bese.fiveam:test :sample
  (it.bese.fiveam:is
   (common-lisp-user::io-equal "6 2
1 2
3 2
4 2
1 6
5 6
"
    "2
"))
  (it.bese.fiveam:is
   (common-lisp-user::io-equal "6 5
1 2
3 2
4 2
1 6
5 6
"
    "0
")))


Measured memory_bytes: 60132