(eval-when (:compile-toplevel :load-toplevel :execute)
  (defparameter OPT
    #+swank '(optimize (speed 3) (safety 2))
    #-swank '(optimize (speed 3) (safety 0) (debug 0)))
  #+swank (progn (ql:quickload '(:cl-debug-print :fiveam))
                 (shadow :run)
                 (use-package :fiveam)))
#+swank (cl-syntax:use-syntax cl-debug-print:debug-print-syntax)

;; BEGIN_INSERTED_CONTENTS
(defmacro split-ints-and-bind (vars string &body body)
  (let ((pos1 (gensym "POS"))
	(pos2 (gensym "POS"))
	(str (gensym "STR")))
    (labels ((expand (vars &optional (init-pos1 t))
	       (if (null vars)
		   body
		   `((let* ((,pos1 ,(if init-pos1 0 `(1+ ,pos2)))
			    (,pos2 (position #\space ,str :start ,pos1 :test #'char=))
			    (,(car vars) (parse-integer ,str :start ,pos1 :end ,pos2)))
		       ,@(expand (cdr vars) nil))))))
      `(let ((,str ,string))
         (declare (string ,str))
	 ,@(expand vars)))))

(deftype non-negative-fixnum () '(integer 0 #.most-positive-fixnum))

(defstruct (union-find
            (:constructor make-union-find
                (size &aux (parents (let ((seq (make-array size :element-type 'non-negative-fixnum)))
                                      (dotimes (i size seq) (setf (aref seq i) i))))
                           (ranks (make-array size :element-type 'non-negative-fixnum
                                                   :initial-element 0)))))
  (parents nil :type (simple-array non-negative-fixnum (*)))
  (ranks nil :type (simple-array non-negative-fixnum (*))))

(declaim (ftype (function * (values non-negative-fixnum &optional)) uf-root))
(defun uf-root (x uf-tree)
  "Returns the root of X."
  (declare (optimize (speed 3))
           (non-negative-fixnum x))
  (let ((parents (union-find-parents uf-tree)))
    (if (= x (aref parents x))
        x
        (setf (aref parents x)
              (uf-root (aref parents x) uf-tree)))))

(declaim (inline uf-unite!))
(defun uf-unite! (x1 x2 uf-tree)
  "Unites X1 and X2 destructively."
  (let ((root1 (uf-root x1 uf-tree))
        (root2 (uf-root x2 uf-tree))
        (parents (union-find-parents uf-tree))
        (ranks (union-find-ranks uf-tree)))
    (cond ((= root1 root2) nil)
          ((< (aref ranks root1) (aref ranks root2))
           (setf (aref parents root1) root2))
          ((= (aref ranks root1) (aref ranks root2))
           (setf (aref parents root2) root1)
           (incf (aref ranks root1)))
          (t (setf (aref parents root2) root1)))))

(declaim (inline uf-connected-p))
(defun uf-connected-p (x1 x2 uf-tree)
  "Checks if X1 and X2 have the same root."
  (= (uf-root x1 uf-tree) (uf-root x2 uf-tree)))

(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)

(defmacro println (obj &optional (stream '*standard-output*))
  `(let ((*read-default-float-format* 'double-float))
     (prog1 (princ ,obj ,stream) (terpri ,stream))))

;; Hauptteil

(defun bridge-p (edge-idx n as bs)
  (let ((tree (make-union-find n)))
    (dotimes (i (length as))
      (unless (= i edge-idx)
        (uf-unite! (aref as i) (aref bs i) tree)))
    (not (apply #'= (loop for i below n collect (uf-root i tree))))))

(defun main ()
  (let* ((n (read))
         (m (read))
         (as (make-array m :element-type 'uint32))
         (bs (make-array m :element-type 'uint32)))
    (dotimes (i m)
      (split-ints-and-bind (a b) (read-line)
        (setf (aref as i) (- a 1)
              (aref bs i) (- b 1))))
    (println
     (loop for i below m
           count (bridge-p i n as bs)))))

#-swank(main)


Measured memory_bytes: 27368