#-swank
(unless (member :child-sbcl *features*)
  (quit
   :unix-status
   (process-exit-code
    (run-program *runtime-pathname*
                 `("--control-stack-size" "256MB"
                   "--noinform" "--disable-ldb" "--lose-on-corruption" "--end-runtime-options"
                   "--eval" "(push :child-sbcl *features*)"
                   "--script" ,(namestring *load-pathname*))
                 :output t :error t :input t))))
;; -*- coding: utf-8 -*-
(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
           #\# #\> (lambda (s c p) (declare (ignore c p)) (read s nil (values) t))))
#+swank (cl-syntax:use-syntax cl-debug-print:debug-print-syntax)
#-swank (disable-debugger) ; for CS Academy

;; BEGIN_INSERTED_CONTENTS
;;;
;;; Topological sort
;;;(declaim (ftype (function * (values fixnum &optional)) read-fixnum))
(defun read-fixnum (&optional (in *standard-input*))
  (declare #.OPT)
  (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 #\-))
                                  (setf 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))))))))


(define-condition cycle-detected-error (simple-error)
  ((graph :initarg :graph :reader cycle-detected-error-graph)
   (vertex :initarg :vertex :reader cycle-detected-error-vertex))
  (:report
   (lambda (condition stream)
     (format stream "Detected a cycle containing ~A in ~A."
             (cycle-detected-error-vertex condition)
             (cycle-detected-error-graph condition)))))

(defun topological-sort (graph)
  "Returns a topologically sorted array of all the vertex in GRAPH. This
function signals CYCLE-DETECTED-ERROR when it detects a cycle.

GRAPH := vector of adjacency lists."
  (declare ((array list (*)) graph))
  (let* ((n (length graph))
         (tmp-marked (make-array n :element-type 'bit :initial-element 0))
         (marked (make-array n :element-type 'bit :initial-element 0))
         (result (make-array n :element-type '(integer 0 #.most-positive-fixnum)))
         (index (- n 1)))
    (declare (fixnum index))
    (labels ((visit (v)
               (when (= 0 (aref marked v))
                 (when (= 1 (aref tmp-marked v))
                   (error 'cycle-detected-error :graph graph :vertex v))
                 (setf (aref tmp-marked v) 1)
                 (dolist (next (aref graph v))
                   (visit next))
                 (setf (aref marked v) 1)
                 (setf (aref result index) v)
                 (decf index))))
      (dotimes (v n result)
        (when (= 0 (aref marked v))
          (visit v))))))

(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
;;;

(declaim (inline encode))
(defun encode (x y)
  (when (> x y)
    (rotatef x y))
  (dpb y (byte 10 10) x))

(defconstant +max+ (ash 1 20))

(defun main ()
  (let* ((n (read))
         (as (make-array (list n (- n 1)) :element-type 'uint32))
         (graph (make-array +max+ :element-type 'list :initial-element nil)))
    (dotimes (i n)
      (dotimes (j (- n 1))
        (let ((a (- (read-fixnum) 1)))
          (setf (aref as i j) a))))
    ;; #>as
    (dotimes (i n)
      (dotimes (j (- n 2))
        (let* ((op1 (aref as i j))
               (op2 (aref as i (+ j 1)))
               (v1 (encode i op1))
               (v2 (encode i op2)))
          (push v2 (aref graph v1)))))
    ;; #>(subseq graph 0 1000)
    (handler-bind ((cycle-detected-error (lambda (c) (println -1) (return-from main))))
      (let ((seq (topological-sort graph))
            (dp (make-array +max+ :element-type 'uint32 :initial-element 1)))
        ;; #>seq
        (dotimes (i +max+)
          (let ((v (aref seq i)))
            (dolist (neighbor (aref graph v))
              (setf (aref dp neighbor)
                    (max (aref dp neighbor)
                         (+ 1 (aref dp v)))))))
        (println (reduce #'max dp))))))

#-swank (main)


Measured memory_bytes: 62776