(in-package :cl-user)
(eval-when (:compile-toplevel :load-toplevel :execute)
  (defparameter *opt*
    #+swank '(optimize (speed 3) (safety 2))
    #-swank '(optimize (speed 3) (safety 0) (debug 0)))
  #+swank (ql:quickload '(:cl-debug-print :fiveam :cp/util) :silent t)
  #+swank (use-package :cp/util :cl-user)
  #-swank (set-dispatch-macro-character
           #\# #\> (lambda (s c p) (declare (ignore c p)) `(values ,(read s nil nil t))))
  #+sbcl (dolist (f '(:popcnt :sse4)) (pushnew f sb-c:*backend-subfeatures*))
  #+sbcl (setq *random-state* (seed-random-state (nth-value 1 (get-time-of-day)))))
#-swank (eval-when (:compile-toplevel)
          (setq *break-on-signals* '(and warning (not style-warning))))
#+swank (set-dispatch-macro-character #\# #\> #'cl-debug-print:debug-print-reader)

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

(defconstant +mod+ 1000000007)

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

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

;; BEGIN_INSERTED_CONTENTS
(defpackage :cp/read-fixnum
  (:use :cl)
  (:export #:read-fixnum))
(in-package :cp/read-fixnum)

(declaim (ftype (function * (values fixnum &optional)) read-fixnum))
(defun read-fixnum (&optional (in *standard-input*))
  "NOTE: cannot read -2^62"
  (macrolet ((%read-byte ()
               `(the (unsigned-byte 8)
                     #+swank (char-code (read-char in nil #\Nul))
                     #-swank (sb-impl::ansi-stream-read-byte in nil #.(char-code #\Nul) nil))))
    (let* ((minus nil)
           (result (loop (let ((byte (%read-byte)))
                           (cond ((<= 48 byte 57)
                                  (return (- byte 48)))
                                 ((zerop byte) ; #\Nul
                                  (error "Read EOF or #\Nul."))
                                 ((= byte #.(char-code #\-))
                                  (setq minus t)))))))
      (declare ((integer 0 #.most-positive-fixnum) result))
      (loop
        (let* ((byte (%read-byte)))
          (if (<= 48 byte 57)
              (setq result (+ (- byte 48)
                              (* 10 (the (integer 0 #.(floor most-positive-fixnum 10))
                                         result))))
              (return (if minus (- result) result))))))))

;;;
;;; Disjoint set (union by size & path compression)
;;;

(defpackage :cp/disjoint-set
  (:use :cl)
  (:export #:disjoint-set #:make-disjoint-set #:ds-data
           #:ds-root #:ds-unite! #:ds-connected-p #:ds-size #:ds-clear))
(in-package :cp/disjoint-set)

(defstruct (disjoint-set
            (:constructor make-disjoint-set
                (size &aux (data (make-array size :element-type 'fixnum :initial-element -1))))
            (:conc-name ds-)
            (:predicate nil)
            (:copier nil))
  (data nil :type (simple-array fixnum (*))))

(declaim (inline ds-root))
(defun ds-root (disjoint-set x)
  "Returns the root of X."
  (declare ((mod #.array-total-size-limit) x))
  (let ((data (ds-data disjoint-set)))
    (labels ((recur (x)
               (if (< (aref data x) 0)
                   x
                   (setf (aref data x)
                         (recur (aref data x))))))
      (recur x))))

(declaim (inline ds-unite!))
(defun ds-unite! (disjoint-set x1 x2)
  "Destructively unites X1 and X2 and returns true iff X1 and X2 become
connected for the first time."
  (let ((root1 (ds-root disjoint-set x1))
        (root2 (ds-root disjoint-set x2)))
    (unless (= root1 root2)
      (let ((data (ds-data disjoint-set)))
        ;; NOTE: If you want X1 to always be root, just delete this form. (Time
        ;; complexity becomes worse, however.)
        (when (> (aref data root1) (aref data root2))
          (rotatef root1 root2))
        (incf (aref data root1) (aref data root2))
        (setf (aref data root2) root1)))))

(declaim (inline ds-connected-p))
(defun ds-connected-p (disjoint-set x1 x2)
  "Returns true iff X1 and X2 have the same root."
  (= (ds-root disjoint-set x1) (ds-root disjoint-set x2)))

(declaim (inline ds-size))
(defun ds-size (disjoint-set x)
  "Returns the size of the connected component to which X belongs."
  (- (aref (ds-data disjoint-set)
           (ds-root disjoint-set x))))

(declaim (inline ds-clear))
(defun ds-clear (disjoint-set)
  "Deletes all connections."
  (fill (ds-data disjoint-set) -1)
  disjoint-set)

;; BEGIN_USE_PACKAGE
(eval-when (:compile-toplevel :load-toplevel :execute)
  (use-package :cp/disjoint-set :cl-user))
(eval-when (:compile-toplevel :load-toplevel :execute)
  (use-package :cp/read-fixnum :cl-user))
(in-package :cl-user)

;;;
;;; Body
;;;

(defun main ()
  (let* ((n (read))
         (m (read))
         (col-boxes (make-array n :element-type 'list :initial-element nil))
         (dset (make-disjoint-set m))
         (res 0))
    (dotimes (i n)
      (let ((b (- (read-fixnum) 1))
            (c (- (read-fixnum) 1)))
        (push b (aref col-boxes c))))
    (dotimes (c n)
      (loop for (b1 b2) on (aref col-boxes c)
            while b2
            do (ds-unite! dset b1 b2)))
    (dotimes (b m)
      (when (= (ds-root dset b) b)
        (let ((size (ds-size dset b)))
          (incf res (- size 1)))))
    (println res)))

#-swank (main)

;;;
;;; Test
;;;

#+swank
(progn
  (defparameter *lisp-file-pathname* (uiop:current-lisp-file-pathname))
  (setq *default-pathname-defaults* (uiop:pathname-directory-pathname *lisp-file-pathname*))
  (uiop:chdir *default-pathname-defaults*)
  (defparameter *dat-pathname* (uiop:merge-pathnames* "test.dat" *lisp-file-pathname*))
  (defparameter *problem-url* "https://yukicoder.me/problems/no/1390"))

#+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)))

#+(and sbcl (not swank))
(eval-when (:compile-toplevel)
  (when sb-c::*undefined-warnings*
    (error "undefined warnings: ~{~A~^ ~}" sb-c::*undefined-warnings*)))

;; To run: (5am:run! :sample)
#+swank
(5am:test :sample
  (5am:is
   (equal "2
"
          (run "5 4
1 1
2 2
3 2
3 3
4 3
" nil)))
  (5am:is
   (equal "0
"
          (run "5 5
1 1
2 2
2 3
3 4
3 5
" nil)))
  (5am:is
   (equal "4
"
          (run "15 10
1 7
3 15
4 1
3 3
9 4
9 14
6 3
9 7
10 11
2 10
10 13
9 8
5 9
2 13
4 13
" nil))))